07-20-2010, 09:25 AM
While there have been some considerable advances in engine-building technology over the past 30 years, one of the most important lessons we can learn is that it’s the small details that can make or break an engine-building project. The two most important details are checking clearances and triple-checking your work. Far too many of us are not attentive enough to detail, and we learn some hard and expensive lessons — when an overlooked rod bolt fails half way down the track, or when a carelessly seated valve keeper escapes at high revs, destroying the piston and cylinder wall below in less than a second. These are the kinds of important details we don’t want you to miss during your budget engine build.
Lack of proper planning is another reason for the demise of many an engine project. Wise planning is the most important tool you should use in your project. Before heading off to the speed shop, ask yourself the all-important question, “What do I want from this engine?”, then do the plan.
Part of doing the plan is knowing exactly what you can afford, then not giving in to ego and the temptation to spend more than you have. That’s the mistake many of us make along the way. We tend to want to impress our peers, the machine shop, and especially the significant other, but these are the wrong reasons to build an engine. Don’t build an engine to impress anyone besides yourself because you’re the one who has to live with the result. If you’ve overspent, then you can count on grief when it’s time to pay the monthly bills. This is why we stress staying within your budget.
Most of us overbuild our engines. We build more engine than our Ford needs, which costs unnecessary time and money. For example, if you’re building a 1965 Mustang and you want it to be the fastest thing around, your first thought might be to build a 351W stroker that displaces 427ci. Future plans include fuel injection and a supercharger. Just imagine, the power of a big block in a lightweight stallion, but is it more than your Mustang (and your driving skills) can handle? You don’t have to worry about impressing us. We’ve been there, too, and we understand the drawbacks of overbuilding. This is why we’re sharing the cold, hard facts of engine building with you — so you don’t make the same mistakes.
Too many enthusiasts build more engine than a car can safely handle. When we infuse big-block displacement power into a lightweight Mustang, Falcon, or Fairlane, we’re not thinking about the engine and vehicle as a package. Most of us get it backwards. We build a powerful engine, then we wonder how to manage all that power safely. It is better to build the car first, then the engine, because too much power in an unprepared platform can get you maimed or killed. A well-thought-out platform will have good brakes, a handling package, traction enhancement, the right tires and wheels, a rear axle that can take the punishment, and a mature driver who understands all of this.
The goal of this book is to teach you how to build a reliable, affordable engine that will make the power you need. No matter the formula, one basic principle is constant: Performance level is tied directly to budget. The greater the budget and know-how, the faster you will go.
You are not going to make a 600-horsepower small block for $2,500. However, you can build a healthy 350-horsepower small block for approximately $2,500 to $3,000 that will serve you reliably. Keep your expectations and planning realistic. Then go work your plan with perseverance.
PLANNING YOUR BUILD
Before you even start to plan, you must decide what you can reasonably spend on your build. Believe it or not, if you do your homework and learn how to do much of the work yourself,
you can get into a fresh engine for approximately $2,500. Even if you have never done it before, building an engine is not difficult if you pay close attention to detail. Engine assembly is costly if
you farm it out. Machine work is also expensive, but most of us don’t have the necessary equipment or the know-how to do it ourselves. Engine assembly boils down to having the right tools and a super clean shop environment. Certain tools, like the torque wrench, piston ring compressor, micrometer, and dial indicator, can be rented locally. You will only need these items for a weekend, which makes them affordable.
TOOLS OF THE TRADE
When you’re new to the world of engines, it is easy to get carried away in the tool department. After all, we need all those things to get the job done, right? That first trip to Sears is often like a first trip to the speed shop. You lay down the credit card and come home with a wealth of goodies, but they don’t always apply to building an effective engine.
We suggest Sears Craftsman tools because they have a lifetime warranty, great reputation, and there’s a Sears store in nearly every area of the world. The Craftsman warranty is written with no nonsense and no fine print. Bust a socket and Sears will replace it with no questions asked. Strip out a ratchet and Sears will hand you a new one or rebuild your old one. Sears Craftsman tools are the best tool value going. The next best tool value is Husky in the “bang for the buck” department. You can find Husky tools at many home improvement or hardware stores for even less than Craftsman, yet with the same no nonsense lifetime warranty.
Our Beginner’s Tool Shopping List is intended to get you started and will last you the rest of your life with care. It is even something you can pass along because, with proper care, it will last several lifetimes. Most of us buy socket sets, but we forget to go for the deep-well sockets, which you will need in the course of an engine build. One other thing to keep in mind, opt for 6-point sockets, not 12-point. A 6-point socket won’t strip a bolt head and provides a firm grip. Make sure your socket sets have at least two extensions — one 3-inch and one 7-inch. Spring for the universal adapter as well for easy access. If you can afford it, buy a matching set of 12-point shallow and deep-well sockets because they do have a purpose with some engine applications.
When you’re shopping for screwdrivers, hold one in your hand first. You want a screwdriver that feels good in your hand and offers adequate grip comfort and mechanical advantage. If your hand slips around the handle, then it is a poor design. The tip should be super tough steel that will not strip out or break. Go the extra mile and invest wisely now in a screwdriver that will last you a lifetime. Another idea is to buy screwdrivers with bright orange handles for visibility and safety. This lessens the chance of leaving tools where they don’t belong.
We push the idea of quality tools because there really is a difference. Inexpensive wrench sets you can buy for around $10 won’t get the job done effectively. A low-quality forged or casting will strip out and leave you hanging on a Sunday afternoon when you need it most. With Sears Craftsman (and this is not a commercial endorsement), Husky, MAC, or Snap-On tools, you get a lifetime warranty that’s good for as long as the tool exists — for you, your child, your grandchild, great grandchild, and more. MAC and Snap-On tools tend to be very expensive and available only off a truck at better garages everywhere, which makes Craftsman and Husky a better value and easier to find.
Proper tool care once you’ve made the investment is what assures you reliability in the future. Keep your tools clean and serviceable. Lubricate ratchets periodically with engine oil or white grease for best results. Drill bits should be sharpened periodically. When you’re using a drill, run the bit slow and keep it wet with lubrication while drilling. Drill bits begin to squeak whenever they’re dull. Invest in a drill-bit sharpener or find a reliable shop that sharpens drill bits. Most shops that sharpen lawnmower blades and chain saws can sharpen your bits.
It’s also important to know when it’s time to retire tools. Tools that are not serviceable can be dangerous. A loose hammer head, for example, could rearrange yours or someone else’s dental work — or break a window. Cracked sockets, worn wrenches, busted screwdriver handles, stripped ratchets, and other forms of serious tool deterioration are reasons to invest in fresh equipment. It is about your safety and the integrity of your work.
RENTING TOOLS
There are many tools you will only use during an engine build that are expensive. It may be more cost-efficient for you to rent these items. Most shops make rental tools available. Look for the “multi-purpose” in any tool you’re thinking about renting. If you expect to use the tool again, it may well be worth the investment to purchase it now. When renting tools, rent only at the time you intend to use them. Don’t rent every tool mentioned here at the same time because you’re not going to use all of them at the same time.
When renting torque wrenches, keep in mind they are typically either beam or breakaway types. We suggest the breakaway type that “clicks” when the specified torque is reached. Be sure to learn how to properly use a breakaway torque wrench. Ask for instructions when you rent the tool. Keep in mind two things: First, never use a torque wrench to remove a bolt or nut, as you will disturb the calibration. Second, never overtorque a fastener. When you torque a fastener, you are stretching the bolt stock. Too much torque and you stress the fastener. Specified torque readings are there to ensure fastener integrity.
Piston ring compressors are available in different forms. The most common type available to rent is an adjustable type. There is also a ratcheting type that makes piston installation a snap. Custom-sized billet ring compressors are costly and not for the novice.
Harmonic balancer pullers are a borderline rental item. This is something you may use again and again. They don’t cost that much to buy, which is what makes them a borderline item. Balancer pullers also make great steering wheel pullers.
There are two basic types of valve spring compressors -- one you use in the shop on a head in the raw (looks like a huge C-clamp) and one you use with the head installed (more like a pry bar used only for ball/stud fulcrum rocker arm applications). For engine rebuilding, you’re going to need the C-clamp type. You can sometimes pick these up at a discount house for less than it would cost to rent one for several days.
Freeze plug and seal drivers are one of those borderline items you could use again and again. You an also use a like-sized socket as a driver on the end of an extension. This saves money, but could damage the socket. Don’t be a tool abuser.
Thread chasers are a vital part of any engine build because you want clean threads. Clean threads yield an accurate torque reading when it’s time to reassemble the engine. Thread chasing should be performed when the block returns from the machine shop clean, machined, and ready for assembly. Machine shops that are on the ball will have already chased your threads. However, thread chasing is time consuming and machine shops don’t generally do this unless asked and paid for the service. If you do it yourself, it’s a good idea to chase every bolt hole. When a thread chaser is outside of your budget, use Grade 8 bolts and other fasteners with WD-40 to chase the threads. This may sound crude, but it will save you money and get the job done.
Engine stands are one of those purchase/rent questions because renting can sometimes cost you more than simply buying. Harbor Freight Salvage has some of the best values going at $50 to $100 for a stand. If you’re building a heavy big block, don’t cut corners here. Invest in a four-legged engine stand for stability and safety. The low-buck $50 stand will not hold up under the weight of a 650-pound big block. You don’t even want to think about what happens when an engine stand fails — it’s sudden, noisy, and destructive.
The decision to rent or buy tools boils down to how often you will use the tool and how long you will need the tool during your engine build. Any time you’re going to need the tool longer than 1 - 3 days, you’re probably better off buying. If you have to buy, look on the bright side. You can always loan it to friends or sell it after your engine is finished. Keeping it makes it a useful piece of community property among friends.
KEEP A CLEAN SHOP
We cannot stress enough the importance of keeping a clean, organized shop. Do your engine teardown work where you can catalog everything and keep it in its rightful place. Keep engine parts and fasteners in jars or plastic containers that are labeled. Haul the block, heads, crankshaft, and connecting rods to a machine shop immediately upon disassembly. This avoids any confusion and keeps you rolling. If you cannot afford the machine shop at the time, leave the engine assembled until you are ready. We speak from experience on this one because too much is lost both mentally and physically once the engine is disassembled. Keep disassembling, cleaning, machine work, and assembly as cohesive as possible.
It is always a good idea to keep an engine project organized from planning to completion. Know what you’re going to do and when you’re going to do it. Then get busy and see your engine project through to completion. Nothing is more discouraging than a disassembled engine that’s going nowhere because you didn’t have a plan.
Making Power
There is plenty of folklore about making power, such as the myth that it’s easier to make power with a Chevrolet than with a Ford. Nonsense. The truth is, you can make just as much power with a Ford, for the same amount of money, that you can with a Chevrolet. There is no black magic here — just the simple physics of taking thermal expansion and turning it into rotary motion.
To learn how to make power with a given engine, we have to understand how power is made. How much power an engine makes depends on how much air and fuel we can pump through the engine, and on what we do with that fuel and air mixture during the split second it is in the combustion chambers.
We have to think of an internal combustion engine as an air pump. The more air and fuel we can pump through the cylinders, the more power we’re going to make. This is why racers use big carburetors, manifolds, heads, superchargers, turbochargers, and nitrous oxide. Racers understand this air pump theory and practice it with wreckless abandon, sometimes with catastrophic results. Good racers also understand the “too much of a good thing” theory. Sometimes it can cost you a race, and sometimes it can cost you an engine.
Getting power from our air pump takes getting liberal amounts of air and fuel into the chambers, then squeezing the mixture as hard as we can without damaging the engine. When we raise compression, we increase the power of our mixture yields. It is the intense heat of compression coupled with the ignition system spark that yields the energy from our mixture. The more compression we have, the greater the heat created to ignite the mixture.
However, when there’s too much compression and with the resulting heat, the air/fuel mixture can ignite prematurely resulting in preignition and detonation. So we have to achieve the right compression ratio to get the most from the fuel we have. Today’s street fuels won’t tolerate much over 10.5:1 compression. This means we have to look elsewhere for answers in the power equation, like more aggressive camshaft profiles, better heads, port work, hotter ignition systems, exhaust headers that breathe better, state-of-the-art intake manifolds and carburetors, even electronic-fuel injection where we never thought of using it before.
The thing to remember about gasoline engines is this: The fuel/air mixture does not explode in the combustion chambers, it “lights off” just like your gas furnace or water heater. Because the mixture is compressed and ignited, it lights off more rapidly. Combustion in a piston engine is just that, a quick fire that sends a flame front across the top of the piston. Under ideal circumstances, the flame front will travel smoothly across the piston dome, yielding heat and pressure that act on the piston and rod to yield rotary motion at the crankshaft. A bad “light off” that originates at two opposing points in the chamber is the preignition or detonation that we mentioned earlier. The opposing light offs collide creating a shock that hammers the piston dome which is the pinging or spark knock we hear under acceleration. The objective is to get a smooth, quick fire, with the flame front traveling in one, smooth direction for maximum power. Call this power management.
Power management is having the right balance of ignition timing, fuel mixture, compression ratio, valve timing events, and even external forces like blower boost or nitrous input. All of these elements have to work together if we’re to make productive power. Let’s talk about some of the elements we need to make power.
Nitrous oxide or “squeeze” is all the rave today for those looking for quick and easy power (50 to 150 horsepower) on demand. Nitrous makes boatloads of power at the touch of a button, but it can be very harmful to a budget engine that isn’t properly prepared. Nitrous will severely damage your pistons and rings if not properly executed. It can and does hammer rod bearings resulting in severe wear. It is also hard on main bearings due to these loads. No matter what the nitrous oxide optimist club will tell you about “laughing gas”, nitrous can and does shorten engine life. So don’t be drawn into believing it’s a magic horsepower pill without consequences. If you’re going to be using nitrous oxide, be prepared for its shortcomings. Accept the fact that nitrous will shorten engine life no matter how it is used. The more aggressively you use nitrous, the shorter your engine will live.
It is easy to be lulled into believing a larger carburetor, more aggressive camshaft, and large port heads will make more power but this isn’t always true, especially in budget street engines. Induction, camshaft, and heads should always jibe with your performance mission. What’s more, you want your engine to survive while making all that power. Your engine build plan needs to include a common sense approach that involves the right selection and packaging of parts for best results.
If you’re building a daily driver, you’re going to have to compromise to some degree in terms of performance if you want reliability. We compromise because radical engines don’t do well for the daily commute. They also struggle to pass a smog check, depending on where you live. Radical camshaft profiles give the engine a rough idle, which can be frustrating in traffic and make it virtually impossible to pass a smog check. Loud mufflers can cause hearing damage and make for an annoying drive. They can also get you a ticket for noise pollution in some communities. A high compression ratio can cause overheating when traffic comes to a stop. Overcarburetion fouls spark plugs and pollutes the air.
This brings us to another valid point -- air pollution. Environmentalists and performance enthusiasts don’t get along, but it is our responsibility as performance buffs to build and tune our engines for cleaner emissions and better human health. This doesn’t mean you have to go out and buy catalytic converters and a smog pump. It does mean you need to package your induction and ignition systems for optimum emissions performance at the tail pipe. In short, clean up your performance act.
Carburetors play a role in pollution, too. A big, fat 750 or 850cfm Holley carburetor looks good at the drag strip, cruising spot and car show, but it is not a practical carburetor for everyday street use where clean emissions are important. This isn’t so much about Holley carburetors as it is about carburetor sizing in general. We want carburetor size and engine mission to be compatible for optimum performance and cleaner emissions.
If you think this clean emissions hoopla is a lot of nonsense, consider the last time you were behind a hopped up vintage musclecar in traffic that made your eyes water. Also remember that if your vehicle falls under the guidelines of state emission laws and smog checks, the law doesn’t give you a choice. Clean up your exhaust emissions or face revocation of your license plates in some states.
Building an environmentally responsible engine doesn’t have to be difficult either. Carbureted engines are not going to burn as clean as fuel-injected versions. If you can run electronic fuel injection, do so for cleaner air. Do so for your own health and for the sake of others who breathe. If you can’t, be conservative in your performance plan and dial in the right size carburetor.
Instead of a 750 or 850cfm carburetor, opt for a 600 or 650cfm carb and see how your engine performs. A carburetor that’s too small will become apparent quickly in the absence of torque as RPMs increase. Large carburetors give us more torque on the high end. Smaller carburetors do well on the low end. Choosing the right amount of carburetion is often trial and error.
Keep proper carburetor jetting in mind, too. Jets that are too large will make the engine run rich or “fat”, burning the eyes of those who have to follow you. Jets that are too small can be harmful if you’re leaning on it hard and lean detonation burns a hole in a piston. Again, fine tune carburetor and jet sizing for best results. Always err on the side of rich versus lean for longer engine life. If you really want to make a lasting impression on the community, go for a smog check each time you make a carb/jet change and see what it does for emissions. Cleaner air is up to all of us.
PLAN FOR POWER
The important question is, how much power do you want your engine to make and what can you afford? We’re assuming you have invested wisely in your engine’s bottom end with healthy parts and building procedures that will make the most of the engine’s potential. For example, if your plan is 450 to 500 horsepower from a small block, stock rods and cast pistons won’t cut it. Ask yourself what your engine’s bottom end can withstand, and then program the power accordingly. If you are seeking 450 horsepower, then hopefully you have prepared the bottom end with heavy-duty rods and pistons, coupled with building techniques to ensure that your engine survives.
Making power in a Ford engine has everything to do with air flow. A popular misconception suggests that the larger the carburetor, intake, and cylinder head ports, the more power you are going to make. In part, this is true. However, you must ask, where do you want the engine to make power and why? If you are building a drag or circle-track racer, you are going to want the engine to behave differently than you would a street engine. Racing engines make their power in a much higher RPM range than a street engine. A circle-track racing engine is going to make power differently than a drag-racing engine. Torque needs to come on strong from part throttle to full throttle with a circle-track engine. Drag-racing engines need to make torque at high revs. In either case, we have to design an engine that delivers power when it’s needed or the whole thing is pointless.
[attachment=1936]
Have you invested in a strong bottom end? Before you can make real power, you should have a bottom end that can handle the power. All that power is useless if you have a soft bottom end. Failure should never be an option.
A good street engine should make excellent low-end torque, yet be snappy when it’s time to wind it tight. With that in mind, which carb, manifold, cylinder heads, and camshaft should you choose? First, you’re going to want cylinder heads that are compatible with your pistons. With flat-top pistons (which most street engines should have), the field is wide open. If you’re opting for stock cylinder heads, keep combustion chamber size and deck thickness in mind. Nothing beats older Ford cylinder heads for compression, thanks to smaller chambers. An early 289/302 small-block cylinder head with 57cc chambers, coupled with flat-top pistons, will yield a compression ratio of approximately 10.0:1 depending upon compression height. Late-model 302 heads with 64cc chambers will yield less compression, which may mandate shaving the block and head deck surfaces to achieve the 10.0:1 ratio desired. Keep this in mind when shopping cylinder heads.
[attachment=1937]
Making power has everything to do with airflow. Where do you want your engine to make power? Where will your engine’s power band be most of the time? Large ports, such as those found in this 351C-4V head, have little value in daily street use. Huge ports do their best work at high RPM, where we need lots of airflow. For low-end torque, we need smaller ports where air velocity increases at lower revs, giving us all-important torque where we need it most.
Cylinder Block
The foundation for an engine build is the cylinder block. Whether it’s a small or big block, selecting the proper block for your build is the single greatest decision you will make aside from choosing the right machine shop. Depending on the block you need, selecting the right one can often be a great challenge. For example, a four-bolt main Boss 302 block will be a lot tougher to find than a garden-variety 302 block. Likewise, a 427 cross bolt will be more of a challenge to locate than a 390 block. In this section, we’re going to show you how to choose a block. We’re also going to show you how to tear down, inspect, and build one.
When you’re shopping for a block, close inspection is vital. The cylinder bores should be sized before you go any further. Small-block Fords should never be bored beyond .040-in. oversize. Some builders have gone to .060-in. oversize, but this is not recommended. If a block is already at .030-in. oversize, you may have .010 in. more to play with. If bore taper is greater than an .011-in. variance, find another block because the only overbore choice then is .060-in. oversize. Three exceptions to the small-block overbore limit are the 351C, 351M, and 400M. These blocks can be bored to .060-in. oversize if they have already been bored .030-in. or .040-in. Big blocks, with the exception being the FE-series 427, can be bored to .060" oversize. The 427’s limit is .030" oversize, and this is marginal.
While you’re shopping for blocks, we suggest having the block sonic tested for cracking and other irregularities. Sonic testing finds irregularities in the casting the human eye cannot see. Some Ford blocks, such as the 351C, 351M, and 400M, are notorious for cracking. Cracking is hard to see even with an antiseptic casting. Sonic testing can be expensive, but it beats the costly mistake of cleaning and machining a block only to discover it is cracked later.
[attachment=1938]
[attachment=1939]
Your initial block inspection should reveal obvious defects like cracks, damaged threads, damage to the cast iron or aluminum, scratched or gouged lifter and cylinder bores, flawed decks, welds in the casting, chipped or broken cylinder skirts, etc. Close inspection is important before working your plan.
Some block cracking can be repaired via welding or JB Weld. JB Weld is a two-part catalyzed product that works well with cracked cast iron. Properly mixed and cured, it will last the life of any engine block. For JB Weld to work effectively, you need a clean surface and a crack that has been carefully stop drilled at each end. Just a small 1/16-inch stop drill hole at each end slows and stops cracking. Then weld or JB Weld the crack. We suggest against the use of JB Weld on the cylinder walls and decks where stresses can be extreme. Your machine shop will know best on what call to make on repair. Some blocks are cracked beyond repair.
When you’re putting together a good formula for a block, sometimes you have to opt for different main caps for a stronger build. For example, you can take the main bearing caps from a 289 High Performance block that is beyond salvage and use them on a standard 289/302 block. You can also use main bearing caps from a Mexican block 289/302 for the same purpose because they’re wider and heavier. Along this same thought is the 351C block. You can convert a 351C two-bolt main block to four-bolt mains so long as you have four-bolt main caps from a trashed four-bolt main block. We do this by drilling and tapping the two-bolt main block for four-bolt mains. In the raw, the two-bolt and four-bolt main 351C blocks are basically the same casting.
Main bearing saddle trueness is another important issue facing the budget engine builder. The alignment of the main bearing saddles is rarely a cause for concern during an engine rebuild. Align boring and honing the main bearing saddles can be expensive. But it’s sound judgment. It would be wise for you to have a machine shop check the line bore for proper alignment before going any further. If the block needs to be align bored and honed, it is well worth the cost in terms of increased engine life because it gives the crankshaft a true foundation. Distorted main bearing saddle alignment puts undue stress on the crankshaft, which directly affects wear and tear. The stressed crankshaft alters connecting rod side clearances and puts stress on the main bearings. This can result in shortened engine life due to abnormal wear patterns.
With bore size and line bore out of the way, it is a good idea to check the block for cracks, obstructed water jackets and oil galleries, and other problems. Like we said earlier, cracking is something you don’t want to find after the machine work is finished or the engine is assembled. Finding it early in the game is crucial. Magnafluxing and sonic testing are two means of checking for cracks. Magnafluxing is a simple test easily accomplished by a machine shop. We set up a magnetic field around the suspected area using an electromagnet, then we sprinkle iron powder over the area. Iron particles will collect at the crack, making it easy to see.
Spot checking is yet another means of crack detection. With spot checking, we use a dye and a powder developer to “spot check” cracks. The nice thing about spot checking is the ability to use it on aluminum castings as well as iron. Magnafluxing cannot be used on aluminum castings.
The most common cracking areas are block decks and main bearing webs because these areas are subject to high stress. Check these areas closely and take your time. Block decks become stressed from cylinder head bolt torque plus the high heat and pressure that take place in this area. Main bearing webs are also placed under great stress from bolt/stud torque, plus the horrific loads this area experiences. Use every means available to ensure you’ve found a solid block.
Obstructed coolant passages have created more than their share of headaches for engine builders. Mass engine rebuilders are sometimes guilty of knocking old freeze plugs into the water jackets to speed disassembly. Unfortunately, whoever gets this engine after the fact must deal with overheating issues because those freeze plugs knocked into the jacket obstruct coolant flow and heat dissipation. During disassembly, take a bright light and inspect cooling passages (water jackets) for any obstructions and corrosion. Passages between the heads and block sometimes become clogged with rust and iron particles. Make sure these passages are clear.
Oil galleries can become clogged with sludge, metal particles, and nylon, which starves important moving parts of oil. We mention “nylon” because failed timing sets shed nylon and aluminum particles into the oil pan clogging the pick-up and oil galleries. What’s more, these particles find their way to the main, rod, and cam bearings causing excessive journal wear and engine failure. This is why close inspection of oil galleries is vital to any engine build. You’re going to need a long wire brush, solvent, and water under pressure to ensure all passages are sanitary. If this seems excessive, consider the cost of engine failure and having to do this all over again.
Another area we rarely see addressed is lifter bores, but lifter bore side clearances are vital to oil control and proper lifter function. Lifter bores should be inspected for scratches and nicks, then honed as necessary. Engines that have been sitting for a long time often experience ceased lifters that become welded to the bores. We suggest extreme caution removing the lifters because you can permanently damage the bores. Then inspect the lifter bore for scoring, nicks, and other damage. Ceased lifters can be worked loose with WD-40 (a good soaking) and a pair of vice grips. Lifter bore side clearances should be checked using a new lifter as a reference. Side clearances should be 0.0005 to 0.0020". You may also use a small dial-bore gauge or micrometer to check lifter bore size. Check the bore diameter, then lifter diameter to determine clearance. Remember, all lifter bores should be checked because all wear differently.
BLOCK & CASTING IDENTIFICATION
Ford makes it easy for enthusiasts to identify corporate castings. Please understand that Ford casting numbers aren’t always the same as part or engineering numbers. Identifying a casting is a matter of knowing what Ford part and casting numbers mean. Here’s what you can expect to see.
It’s easy to identify Ford castings once you understand the system because there’s not only a casting number, but a casting date code that tells you exactly when the piece was cast. Not only that, a date code is stamped in the piece which tells the date of manufacture. With these two date codes, we know when the piece was cast and when it was ultimately manufactured.
Ford part numbers can be found in the Ford Master Parts Catalog on microfilm at your Ford dealer or in one of those 900-pound parts catalogs from the good old days. Because Ford has discontinued a great many parts for vintage Fords, these part numbers don’t always exist in present day dealer micro films. This is called “NR” or “not replaced” which means it isn’t available from Ford any longer. However, casting numbers on parts tell us a lot about the piece.
DATE CODES
Date codes can be found two ways in Ford castings. When the four-character date code is cast into the piece, this indicates when the piece was cast at the foundry. When it is stamped into the piece, this indicates the date of manufacture.
Another area of interest to Ford buffs is where the piece was cast or forged. With Ford engines, we’ve seen three foundry identification marks. A “C” circled around an “F” indicates the Cleveland Iron Foundry. “DIF” indicates Dearborn Iron Foundry. “WF” or “WIF” indicates Windsor Iron Foundry. Single and double-digit numbers typically indicate cavity numbers in the mold.
Rotating Assembly
What we build into an engine’s bottom end directly determines durability and lifespan. Believe it or not, you can build integrity into a budget engine if you understand what counts and where to prioritize. Your focus needs to be on areas that do count. This means using the best parts available in your budget range; in short, spending money where it makes the most sense in a budget engine build.
When we’re planning a budget engine, it is wise to plan for the best our budget can buy, then cost down as necessary, prioritizing as we go. For example, you might want a set of Crower Sportsman rods topped with forged pistons. When cost enters the picture, you may have to throttle back to hypereutectic pistons and modified stock rods to get the job done. Compromising down under is something you do carefully, answering yourself honestly what this engine is going to be.
Before you get started, it is important to remember there are no guarantees when we build an engine. Anytime we build an engine, we always run the risk of engine failure due to flawed materials or faulty assembly procedures employed during the build. Additionally, there is the risk of engine failure due to abuse once in service — such as over-revving, poor tuning, or the neglect of proper maintenance like regular oil changes. The best we can do is to put quality into an engine build in the first place, then do our best to treat the mill respectfully once the chambers are warm.
Treating the mill respectfully means using common sense. Never push a cold engine, for example. Cold oil doesn’t flow and coat moving parts as liberally as warm oil. Cold parts need warm-up time to expand to proper tolerances. Operating an engine in a poor state of tune is another factor. Too much timing or a lean fuel mixture is hard on an engine. Too much of either will destroy an otherwise healthy engine in seconds.
FIRST, A WORD ON BALANCING
Before we get into how to build a solid bottom end, we must first talk about
balancing issues and how they pertain to Ford V-8 engines. Proper dynamic balancing is rooted in having the right combination of rotating and reciprocating parts. All Ford small-block engines, including the 351C, 351M, and 400M, are “externally” balanced. This means we counterweight the engine “externally” on the flywheel/flexplate and harmonic balancer to achieve dynamic balance.
Why go outside and externally balance? Because the crankshaft counterweights inside don’t always give us sufficient weight to counter reciprocating bobweight (rods and pistons). We add counterweight to the flywheel and harmonic balancer to make up for the difference in reciprocating weight inside the block. Look at a small-block Ford flywheel, flexplate, and harmonic balancer and you can see the counterweighting. On flexplates, the counterweight is welded on. With flywheels, it’s an integral part of the casting. Holes are drilled in the flywheel, often opposite the counterweight, to achieve ideal dynamic balancing. The same can be said for the harmonic balancer, which is also drilled to achieve ideal dynamic balance. We drill flywheels and harmonic balancers to remove weight where it isn’t needed.
One Ford small block, the 1963-67 289 High Performance V-8, uses additional counterweighting (a slide-on counterweight) at the front of the crankshaft to allow for heavier reciprocating weight inside. If you’re building a replica Hi-Po, you don’t have to have this counterweight. Your machine shop can fill the crankshaft counterweights with Mallory metal or add weight to the flywheel/flexplate.
Why is all this balancing hoopla important? Whenever we’re dynamic balancing an externally balanced engine, we must have the flywheel (manual transmission), flexplate (automatic transmission), and harmonic balancer present at the time of balancing. Horrible vibrations abound when we ignore this fact.
What makes the small-block “external” balance issue more complicated is 28-ounce offset balance versus 50-ounce offset. Earlier Ford small blocks like the 221, 260, 289, and 302 V-8s through 1981 were 28-ounce offset balanced. When Ford began producing the 5.0L (302) High Output V-8 in 1982, a 50-ounce offset balance was used to allow for heavier reciprocating masses inside. Small-block crankshaft flanges are drilled to allow flexplate or flywheel installation one way only. This prevents us from incorrectly installing the flywheel or flexplate, adversely affecting balance.
Ford FE big-blocks were both internally and externally balanced depending on engine type. All FE engines, except the 410 and 428, were internally balanced. Internally balanced means the crank, rods, and pistons are balanced together without concern for the flywheel, flexplate, or harmonic balancer. Internal balancing means there’s enough counterweighting in the crankshaft counterweights to do the job without help from the flywheel, flexplate, or harmonic balancer.
The 410 and 428 were externally balanced because they had greater reciprocating weight than other FE counterparts. Both had heavier rods and pistons, which made it necessary to add counterweighting outside the engine at the flywheel, flexplate, and harmonic balancer. The 428 Cobra Jet has an additional slip-on counterweight at the front of the crankshaft behind the harmonic balancer to allow for heavier moving parts inside.
We’ll take the FE story a step further with the FT (Ford Truck) big-block cousin. If you’re using a cast or steel-forged FT truck crankshaft (affordable brute strength) in your FE engine, always remember FT engines are externally balanced which means the flywheel, flexplate, and harmonic balancer must be included in the balancing process.
All 385-series 429 and 460ci engines are “internally” balanced, which means they don’t need any help outside at the flywheel, flexplate, or harmonic balancer. This is a big plus for the 385 because it makes dynamic balancing easy. When it’s time to replace a clutch and flywheel, you can expect a good balancing experience because the crankshaft, rods, and pistons are independent from the flywheel, flexplate, and harmonic balancer.
STROKER KITS
Pumping up the displacement in your Ford V-8 doesn’t have to be expensive. In fact, when you opt for a cast crankshaft and cast pistons, stroking your budget engine doesn’t have to cost any more than a simple rebuild. Stroker kits are available from Performance Automotive Warehouse (PAW) for not much more than a budget engine kit. Ditto for Summit Racing Equipment and Ford Racing Technology.
An engine is stroked by increasing the distance the piston travels in the cylinder bore. When we increase the distance the piston travels in the bore, the bore takes on more air and fuel resulting in more power. Stroker kits vary in scope and cost. Often you can stroke an engine without buying a kit using off-the-shelf parts. For example, you can stroke a 390 to 410+ci by installing a 428 crankshaft, or turn a 429 into a 460 with a 460 crankshaft. Just offset grind a 302 or 351 crank and use the right rod and piston for increased displacement from your small block.
Stroker kits are the easiest means to displacement when off-the-shelf Ford parts won’t get you there. Ford Racing, for example, offers a 347ci stroker kit (M-6013-B347) for 289/302 blocks. This kit sports a nodular-iron 3.40" stroke crankshaft, KB flattop pistons, Federal Mogul high-performance connecting rods, and Grant piston rings. You must provide all machine work and dynamic balancing. Remember, this is an externally-balanced engine. Flywheel, flexplate, and harmonic balancer must be present for balancing.
Ford Racing also offers a 514ci stroker kit (M-6013-A514) for 429/460 big blocks. This kit includes a nodular-iron crankshaft with 4.30" stroke, M-6200-A514 connecting rods, choice of TRW forged pistons, Speed Pro piston rings, and Federal Mogul bearings. Like the small-block stroker kit mentioned earlier, this kit requires externally balancing with flywheel, flexplate, and harmonic balancer present.
Stroker engines are also available from Ford Racing. You can install 600 horsepower in a weekend with the M-6007-B514 crate 514ci big-block package. This engine has been dyno tested at 600 horsepower at 6,250 rpm, which is 590 ft./lbs. of torque at 4,750 rpm.
Coast High Performance has a variety of stroker kits for Ford V-8s. The most popular is the 347ci Street Fighter small block. Several versions with either I-beam or H-beam rods are available for your application depending on budget. Coast also offers 377, 408, and 426ci stroker kits for 351W and 351C engines. If you’re building a 385-series big block, Coast can help with 501, 514, and 557ci stroker kits for your monster big block.
Keep in mind that when you’re ordering a stroker kit for your Ford V-8, the more expensive kits sport H-beam rods, forged pistons, and steel cranks. Rules of budgetary concern must apply here. Street engines don’t need race-ready pieces. Keep your expectations realistic and an eye on the check book.
Cylinder Heads
You can achieve significant gains in engine power with the proper selection and modification of cylinder heads. Cylinder head port size and shape, coupled with combustion chamber size and shape, determine an engine’s power personality. The “bigger is better” theory most of us have accepted over the years doesn’t always work to an engine’s advantage. A street engine can have too much cylinder head, which adversely affects driveability. The same can be said for racing engines, depending upon the application. Ports that are too large hurt the low-end torque we need for effective street performance. Your challenge is to achieve the right combination of port size and camshaft profile to enhance driving pleasure. You’re going to want a cylinder head/piston/induction/camshaft combination that will serve you well in regular driving as well as traffic light-to-traffic light performance.
How you intend to use the engine directly determines the type of cylinder head you should select. Budget street engines benefit more from the smaller ports we see with stock heads. They don’t always need porting and polishing, either. Sometimes porting and polishing take street power away from where you need it most. Stock intake ports that are rough cast keep fuel droplets in suspension on carburetor equipped engines. This improves low-end torque. Ground and polished intake ports can actually hurt low-end torque on carbureted engines because fuel atomization and suspension are affected.
SMALL BLOCK
One of the biggest myths you will face in your Ford engine build is that the 289 High Performance head is the best head to use. This is not necessarily so. The only difference between the 289 High Performance head and the 2V/4V head is valve spring pockets and screw-in rocker-arm studs. Otherwise, port size is virtually the same. So save your money and spruce up a set of 2V/4V heads or opt for 351W types. How? By doing some port work, opting for screw-in rocker-arm studs, and installing hardened valve seats and larger valves.
If you’re building a 289 High Performance engine, opt for larger 1.94/1.60" Chevrolet valves (no one’s going to know they’re there but you) and a port/bowl job to achieve the most from those factory Hi-Po heads. Externally, they will look stock. Internally, they will help your 289 High Performance engine breathe like it never has before. You can also opt for 351W heads here too without anyone knowing the difference externally.
Vintage small-block Ford head choices aren’t as simple as they may appear. There has been significant change in the 221/260/289/302 head over the past four decades. Some of these heads are best avoided. Others are diamonds in the rough.
The best small-block head to use is the 1969-73 351W, thanks to its larger valves and ports. It’s a bolt-on swap. When a 351W head cannot be sourced, the 1965-73 289/302 head is your best bet, due to its smaller wedge chambers. We stress head use prior to 1974 because combustion chamber size remains smaller in those years, keeping compression healthy.
When you are building a set of heads, good machining technique is important. First, castings should be checked for cracks and serious warpage. Then head deck surfaces should be checked and milled as necessary. Valves and guides should be reworked or replaced. Hardened exhaust valve seats should be installed. Pushrod guide plates and screw-in rocker-arm studs should be fitted. When budget is limited, you should opt for 1965 through early 1966 heads with pushrod guides already cast. If you are running a hot camshaft, screw-in rocker-arm studs become mandatory. When screw-in studs are beyond your budget, pinning the press-in studs becomes an inexpensive alternative.
Bush Performance in Fort Smith, Arkansas offers a low-cost way to get into hot street performance with the Street Boss system (nicknamed the “Clevor”, for Cleveland and Windsor). The Street Boss system puts the 351C head atop the 289/302/351W block. The way you intend to use your engine determines which 351C head you will use. For the weekend racer, the 351C-4V head with its large ports and closed-wedge chambers makes a good high-rev head. The 351C-4V head breathes very well at high RPM like we see in drag and road-course racing. The 351C-2V head is a better street head due to its smaller ports and open-chamber design. Smaller ports give you better low-end torque. Open chambers reduce the risk of detonation with low-octane fuels.
[attachment=1940]
The 1969-73 351W head is a budget performance bolt-on for 289/302ci engines due to its larger valves and ports. The only important difference to watch for is the dog-leg coolant passage between the intake manifold and cylinder head on early 351W heads. This can pose leak problems if you use the wrong intake gasket. Use the 351W intake manifold gasket.
New aftermarket heads aren’t within the realm of a budget build. However, as they age and see use, they often wind up at the swap meets for considerably less than they were new. Glass beading and valve work makes them as good as new for less money. Good street heads include the Ford Motorsport SVO GT-40 iron and aluminum heads, World Products Windsor Jr. heads, and Edelbrock Performers. These are the most common, most reliable heads out there for the builder on a budget.
For those of you building late-model 5.0L and 5.8L engines, cylinder head choices tend to be different, especially if you’re interested in meeting emission standards. From 1982-84, Ford used a D9AE-6049-AA cylinder head casting atop the 5.0L High Output V-8. This is not a high-performance cylinder head although it was used on the 1982-84 5.0L High Output engines. It is, however, a workable cylinder head that will come alive with port work and larger 1.94/1.60" Chevrolet valves.
Small-block Ford heads lost yardage in the performance arena after 1978 with Ford’s increasing attention to emissions and driveability. Ports became smaller for improved low-end torque and cleaner emissions. Although this works well in traffic, it doesn’t do much for our engine in higher RPM ranges. Despite the D9AE casting shortcomings, you can still port these heads and make power. However, this is not maximizing what you can do with a stock cylinder head.
The biggest shortcoming with the D9AE casting is the exhaust port with Ford’s infamous Thermactor injection “hump” in the port. It becomes very restrictive. However, this hump can be ground out and all restriction taken away with some Saturday afternoon labor on a work bench. For 1985 only, Ford went to the E5AE head, which was little more than a modified D9AE casting designed for easy roller tappet removal with the head installed. It is identifiable by the reliefs notched in the head at the lifter valley. Otherwise, it is virtually identical to the D9AE casting.
Ford began making improvements to the 5.0L/5.8L head in 1986 with the “high-swirl/fast burn” E6AE and E6TE castings. This head saw widespread use from 1986-88 depending on vehicle application. A shrouded intake valve was trademark to the “high-swirl/fast burn” concept. Thing is, the E6AE/E6TE head didn’t do much for power.
The E5TE and E7TE heads introduced for 1987 are undoubtedly the best late-model castings because the “high-swirl/fast burn” chamber is eliminated. This is more a return to the 1985 High Output/Truck head with improved water jacket passages. For you the engine builder, this head is good for an easy bonus 25-30 horsepower.
The 1993-95 Cobra GT-40 head is little more than a marine head with larger valves and ports. This fact all by itself makes the GT-40 a good, economical head for 5.0L/5.8L performance. Economical because it is a common head. Just look for 1.84/1.54" valves, “GT” markings, and F3ZE/F4ZE casting numbers. Ford part numbers are F3ZZ-A and F4ZZ-A. These heads are also available from Ford Racing as M-6049-L302. Properly outfitted, these heads use the F3ZZ-6564-A roller rocker arm with a 1.7:1 ratio.
Camshaft and Valvetrain
The camshaft and valvetrain directly determine not only an engine’s personality, but how reliably it will perform throughout its service life. Unfortunately, a lot of folks have more misconceptions about camshafts than they have facts. Hopefully, in the following pages we can set you straight on the myths and get you headed in the right direction.
To understand how to pick a camshaft and valvetrain, you must first understand how it all works. Choosing a camshaft profile must be based on how you want an engine to perform. Are you building a streetable engine where low- and mid-range torque are important? Or are you building a high-performance racing engine that makes peak torque in the high revs? Whatever the application, it is vital for you to choose the right combination of components.
A camshaft manufacturer’s catalog lists dozens of camshaft types for the same type of engine. This is where it gets mighty confusing for the novice. We see words like lift, duration, lobe separation, base circle, lobe centerline angle, and valve overlap. What does all of this information mean and how will it affect your engine’s performance?
CAMSHAFT SHOP TALK
What makes one camshaft different from another? Call it profile. Profile refers to the lobe’s design, dimension, and positioning, as well as its functionality. Functionality refers to when the lobe opens the valve, when it closes the valve, how long it keeps the valve open, and how much it opens the valve. All of these factors influence an engine’s performance.
Following are a few terms that you will hear in the shop when talk turns to camshafts. Lift is the maximum amount a lobe will open a valve. Duration refers to how long the lobe will keep the valve open. Lobe Separation or center line is the time or duration between intake and exhaust valve action. Overlap plays into lobe separation because it is the period when the exhaust valve is closing and the intake valve is opening. The Ramp is the ascending or descending side of the cam lobe coming off the base circle when lift begins to occur. The Flank is the ascending or descending portion of the lobe past the base circle nearest maximum lift. The camshaft’s Base Circle is the portion of the lobe that doesn’t generate lift. The bottom-most portion of the lobe is called the Heel.
Flat-tappet camshafts work differently than roller-tappet camshafts, which means you have to think differently with each type. Flat-tappet camshafts limit what you can do with lobe profile
if you want street-ability. If you want an aggressive profile with flat tappets, you can only go so far with a street engine or suffer with poor drive-ability (rough idle, low manifold vacuum). If
you want an aggressive profile in a street engine, we suggest stepping up to a roller camshaft, which can handle the aggressive profile better using roller tappets.
STREET CAM FACTS
Based on everything we have seen in nearly 30 years of experience, the best street performance cams are ground with a lobe separation between 108 to 114 degrees. When you keep lobe separation around 112 degrees, you improve drive-ability because the engine idles smoother and makes better low-end torque. This is what you want from a street engine. Any time lobe separation is below 108 degrees, idle quality and streetability suffer. However, there is more to it than just lobe separation.
Compression and cam timing must be considered together because one always affects the other. Valve timing events directly affect cylinder pressure. Long intake valve duration reduces cylinder pressure. Shorter duration increases cylinder pressure. Too much cylinder pressure can cause detonation (pinging). Too little and you lose torque. You can count on cam manufacturers to figure stock compression ratios into their camshaft selection tables, which makes choosing a camshaft easier than it has ever been. Plug your application into the equation and you will be pleased with the results most of the time.
The greatest advice we can offer the layman is to be conservative with your cam specs if you want reliability and an engine that will live a long time. Stay with a conservative lift profile (under .500-in. lift). A high-lift camshaft will beat the daylights out of a valvetrain, and will put valve-to-piston clearances at risk. Watch duration and lobe separation closely, which will help you be more effective in camshaft selection. Instead of opening the valve more (lift), we want to open it longer (duration) and in better efficiency with piston timing (overlap or lobe separation).
Always bear in mind what you are going to have for induction, heads, and exhaust. The savvy engine builder understands that in order to work effectively, an engine must have matched components. Cam, valvetrain, heads, intake manifold, and exhaust system must all work as a team. If you are opting for stock heads, your cam profile doesn’t need to be aggressive. Select a cam profile that will give you good low- and mid-range torque. Torque doesn’t do you any good on the street when it happens at 6500 rpm. Choose a cam profile that will make good torque between 2500 and 4500 rpm. Otherwise, you are just wasting engine.
The thing to remember with camshaft selection is how the cam will work with your engine’s cylinder heads. We need to take a close look at valve lift with a particular head and determine effect. Some camshafts will actually lose power with a given head because there’s too much lift or duration. This is why it is important to understand a given cylinder head before choosing a camshaft. You want to seek optimum with any cylinder head/camshaft combination. This means having to really do your homework before making a decision. Part of building a successful budget engine is doing a lot of the homework yourself because you cannot afford a wasteful experience.
What type of fuel do you intend to run in your engine? This also affects camshaft selection. We can actually raise compression if we’re running a mild camshaft profile or using a higher octane fuel. It all has to work together. Camshaft timing events must be directly tied to actually raise compression if we’re running a mild camshaft profile or using a higher octane fuel. It all has to work together. Camshaft timing events must be directly tied to compression ratio. The longer our duration, the lower the cylinder pressure and resulting compression. The shorter the duration, the less air we’re going to bring into the cylinder, which also affects compression. Our objective needs to be the highest compression without detonation, which will harm the engine. With this in mind, we want the most duration possible without compression extremes. Duration is what gives us torque as long as compression is sufficient.
Valve overlap, as we have stated earlier, is the period between exhaust stroke and intake stroke when both valves are slightly open. This occurs to improve exhaust scavenging by allowing the incoming intake charge to push remaining exhaust gasses out via the closing exhaust valve. Were the exhaust valve completely closed, we wouldn’t get scavenging. The greater the overlap in a street engine, the less torque the engine will make down low where we need it most. This is why we want less valve overlap in a street engine and more in a racing engine, which will make its torque at high RPM. Increased valve overlap works best at high RPM.
Street engines need 10 to 55 degrees of valve overlap to be effective torque powerhouses. When valve overlap starts wandering above 55 degrees, torque on the low end begins to go away. A really hot street engine will need greater than 55 degrees of valve overlap, but not much greater. To give you an idea of what we’re talking about, racing engines need 70 to 115 degrees of valve overlap.
[attachment=1941]
Camshaft design can be confusing. Think of the cam lobe in geographical regions as it travels against the lifter: opening ramp, opening flank, nose, closing flank, closing ramp, then the heel. The base circle is the part of the lobe that doesn’t generate lift.
For a street engine, we want valve overlap to maximize torque, which means a conservative approach in the first place. Push overlap as far as you can without compromising torque. We also have to figure in lift and duration with valve overlap to see the complete power picture.
Lobe separation angle is another area of consideration in street cam selection. This camshaft dynamic is chosen based on displacement and how the engine will be used. Rule of thumb is this. Consider lobe separation based on how much displacement and valving you’re going to be using. The smaller the valves, the tighter (fewer degrees) lobe separation should be. However, tighter lobe separation does adversely affect idle quality. This is why most camshaft manufacturers spec their cams with wider lobe separations than the custom grinders.
Duration in a street engine is likely the most important dynamic to consider in the selection process. We increase duration whenever less lift is desired. Why? Because we get air flow into the cylinder bore two ways: lift and duration. We can open the valve more and for less time to get air flow. Or, we can open the valve less and keep it open longer via duration to get air flow. Each way will have a different effect on performance. Duration is determined by how much cylinder head and displacement you have, and how the engine will be used. Excessive duration hurts low-end torque, which is what we need on the street. So we have to achieve a balance by maximizing duration without a loss in low-end torque. We do this by using the right heads with proper valve sizing. Large valves and ports don’t work well at all for street use. Mix in too much duration and you have a real slug at the traffic light.
[attachment=1942]
This is a flat-tappet camshaft. Notice the cam lobe profile (shape). It is more aggressive by nature even with a stock grind. Streetability suffers when lift and duration are increased, making the idle rough and eroding manifold vacuum.
So what does this tell us about duration? Plenty. We want greater duration whenever displacement and valve sizing go up. Increasing duration falls directly in line with torque peak and RPM range. This does not mean we necessarily gain any torque as RPM increases. It means our peak torque simply comes in at a higher RPM range. An example of this is if our engine is making 350 ft./lbs. of torque at 4500 rpm and we increase duration. We may well be making that same amount of torque at 5200 rpm. In short, increased duration does not always mean increased torque.
Compression has a direct effect on what our duration should be. When we’re running greater compression, we have to watch duration closely because it can drive cylinder pressures too high. Sometimes we curb compression and run greater duration depending on how we want to make power. When we have greater duration, our engine is going to make more power on the high end and less on the low end. This is why you must carefully consider duration when ordering a camshaft. Higher compression with a shorter duration helps the engine make torque down low where we need it most in a street engine. The thing to watch for with compression is detonation and overheating. Maximum street compression should be around 10.0:1.
Valve lift is an issue we must think about as it pertains to an engine’s needs. Small blocks generally need more valve lift than big blocks. As we increase lift, generally we increase torque. This is especially important at low- and mid-RPM ranges where it counts on the street. Low-end torque is harder to achieve with a small block because these engines generally sport short strokes and large bores. Your objective needs to be more torque with less RPM if you want your engine to live longer. Revs are what drain the life out of an engine more quickly.
To make good low-end torque with a small block, we need a camshaft that will offer a combination of effective lift and duration. As a rule, we want to run a longer intake duration to make the most of valve lift. We get valve lift via the camshaft to be sure. However, rocker arm ratio is the other half of the equation. The most common rocker arm ratio is 1.6:1, which means the rocker arm will give the valve 1.6 times the lift we have at the camlobe. When we step up to a 1.7:1 ratio rocker arm, valve lift becomes 1.7 times that which we find at the lobe.
Lack of proper planning is another reason for the demise of many an engine project. Wise planning is the most important tool you should use in your project. Before heading off to the speed shop, ask yourself the all-important question, “What do I want from this engine?”, then do the plan.
Part of doing the plan is knowing exactly what you can afford, then not giving in to ego and the temptation to spend more than you have. That’s the mistake many of us make along the way. We tend to want to impress our peers, the machine shop, and especially the significant other, but these are the wrong reasons to build an engine. Don’t build an engine to impress anyone besides yourself because you’re the one who has to live with the result. If you’ve overspent, then you can count on grief when it’s time to pay the monthly bills. This is why we stress staying within your budget.
Most of us overbuild our engines. We build more engine than our Ford needs, which costs unnecessary time and money. For example, if you’re building a 1965 Mustang and you want it to be the fastest thing around, your first thought might be to build a 351W stroker that displaces 427ci. Future plans include fuel injection and a supercharger. Just imagine, the power of a big block in a lightweight stallion, but is it more than your Mustang (and your driving skills) can handle? You don’t have to worry about impressing us. We’ve been there, too, and we understand the drawbacks of overbuilding. This is why we’re sharing the cold, hard facts of engine building with you — so you don’t make the same mistakes.
Too many enthusiasts build more engine than a car can safely handle. When we infuse big-block displacement power into a lightweight Mustang, Falcon, or Fairlane, we’re not thinking about the engine and vehicle as a package. Most of us get it backwards. We build a powerful engine, then we wonder how to manage all that power safely. It is better to build the car first, then the engine, because too much power in an unprepared platform can get you maimed or killed. A well-thought-out platform will have good brakes, a handling package, traction enhancement, the right tires and wheels, a rear axle that can take the punishment, and a mature driver who understands all of this.
The goal of this book is to teach you how to build a reliable, affordable engine that will make the power you need. No matter the formula, one basic principle is constant: Performance level is tied directly to budget. The greater the budget and know-how, the faster you will go.
You are not going to make a 600-horsepower small block for $2,500. However, you can build a healthy 350-horsepower small block for approximately $2,500 to $3,000 that will serve you reliably. Keep your expectations and planning realistic. Then go work your plan with perseverance.
PLANNING YOUR BUILD
Before you even start to plan, you must decide what you can reasonably spend on your build. Believe it or not, if you do your homework and learn how to do much of the work yourself,
you can get into a fresh engine for approximately $2,500. Even if you have never done it before, building an engine is not difficult if you pay close attention to detail. Engine assembly is costly if
you farm it out. Machine work is also expensive, but most of us don’t have the necessary equipment or the know-how to do it ourselves. Engine assembly boils down to having the right tools and a super clean shop environment. Certain tools, like the torque wrench, piston ring compressor, micrometer, and dial indicator, can be rented locally. You will only need these items for a weekend, which makes them affordable.
TOOLS OF THE TRADE
When you’re new to the world of engines, it is easy to get carried away in the tool department. After all, we need all those things to get the job done, right? That first trip to Sears is often like a first trip to the speed shop. You lay down the credit card and come home with a wealth of goodies, but they don’t always apply to building an effective engine.
We suggest Sears Craftsman tools because they have a lifetime warranty, great reputation, and there’s a Sears store in nearly every area of the world. The Craftsman warranty is written with no nonsense and no fine print. Bust a socket and Sears will replace it with no questions asked. Strip out a ratchet and Sears will hand you a new one or rebuild your old one. Sears Craftsman tools are the best tool value going. The next best tool value is Husky in the “bang for the buck” department. You can find Husky tools at many home improvement or hardware stores for even less than Craftsman, yet with the same no nonsense lifetime warranty.
Our Beginner’s Tool Shopping List is intended to get you started and will last you the rest of your life with care. It is even something you can pass along because, with proper care, it will last several lifetimes. Most of us buy socket sets, but we forget to go for the deep-well sockets, which you will need in the course of an engine build. One other thing to keep in mind, opt for 6-point sockets, not 12-point. A 6-point socket won’t strip a bolt head and provides a firm grip. Make sure your socket sets have at least two extensions — one 3-inch and one 7-inch. Spring for the universal adapter as well for easy access. If you can afford it, buy a matching set of 12-point shallow and deep-well sockets because they do have a purpose with some engine applications.
When you’re shopping for screwdrivers, hold one in your hand first. You want a screwdriver that feels good in your hand and offers adequate grip comfort and mechanical advantage. If your hand slips around the handle, then it is a poor design. The tip should be super tough steel that will not strip out or break. Go the extra mile and invest wisely now in a screwdriver that will last you a lifetime. Another idea is to buy screwdrivers with bright orange handles for visibility and safety. This lessens the chance of leaving tools where they don’t belong.
We push the idea of quality tools because there really is a difference. Inexpensive wrench sets you can buy for around $10 won’t get the job done effectively. A low-quality forged or casting will strip out and leave you hanging on a Sunday afternoon when you need it most. With Sears Craftsman (and this is not a commercial endorsement), Husky, MAC, or Snap-On tools, you get a lifetime warranty that’s good for as long as the tool exists — for you, your child, your grandchild, great grandchild, and more. MAC and Snap-On tools tend to be very expensive and available only off a truck at better garages everywhere, which makes Craftsman and Husky a better value and easier to find.
Proper tool care once you’ve made the investment is what assures you reliability in the future. Keep your tools clean and serviceable. Lubricate ratchets periodically with engine oil or white grease for best results. Drill bits should be sharpened periodically. When you’re using a drill, run the bit slow and keep it wet with lubrication while drilling. Drill bits begin to squeak whenever they’re dull. Invest in a drill-bit sharpener or find a reliable shop that sharpens drill bits. Most shops that sharpen lawnmower blades and chain saws can sharpen your bits.
It’s also important to know when it’s time to retire tools. Tools that are not serviceable can be dangerous. A loose hammer head, for example, could rearrange yours or someone else’s dental work — or break a window. Cracked sockets, worn wrenches, busted screwdriver handles, stripped ratchets, and other forms of serious tool deterioration are reasons to invest in fresh equipment. It is about your safety and the integrity of your work.
RENTING TOOLS
There are many tools you will only use during an engine build that are expensive. It may be more cost-efficient for you to rent these items. Most shops make rental tools available. Look for the “multi-purpose” in any tool you’re thinking about renting. If you expect to use the tool again, it may well be worth the investment to purchase it now. When renting tools, rent only at the time you intend to use them. Don’t rent every tool mentioned here at the same time because you’re not going to use all of them at the same time.
When renting torque wrenches, keep in mind they are typically either beam or breakaway types. We suggest the breakaway type that “clicks” when the specified torque is reached. Be sure to learn how to properly use a breakaway torque wrench. Ask for instructions when you rent the tool. Keep in mind two things: First, never use a torque wrench to remove a bolt or nut, as you will disturb the calibration. Second, never overtorque a fastener. When you torque a fastener, you are stretching the bolt stock. Too much torque and you stress the fastener. Specified torque readings are there to ensure fastener integrity.
Piston ring compressors are available in different forms. The most common type available to rent is an adjustable type. There is also a ratcheting type that makes piston installation a snap. Custom-sized billet ring compressors are costly and not for the novice.
Harmonic balancer pullers are a borderline rental item. This is something you may use again and again. They don’t cost that much to buy, which is what makes them a borderline item. Balancer pullers also make great steering wheel pullers.
There are two basic types of valve spring compressors -- one you use in the shop on a head in the raw (looks like a huge C-clamp) and one you use with the head installed (more like a pry bar used only for ball/stud fulcrum rocker arm applications). For engine rebuilding, you’re going to need the C-clamp type. You can sometimes pick these up at a discount house for less than it would cost to rent one for several days.
Freeze plug and seal drivers are one of those borderline items you could use again and again. You an also use a like-sized socket as a driver on the end of an extension. This saves money, but could damage the socket. Don’t be a tool abuser.
Thread chasers are a vital part of any engine build because you want clean threads. Clean threads yield an accurate torque reading when it’s time to reassemble the engine. Thread chasing should be performed when the block returns from the machine shop clean, machined, and ready for assembly. Machine shops that are on the ball will have already chased your threads. However, thread chasing is time consuming and machine shops don’t generally do this unless asked and paid for the service. If you do it yourself, it’s a good idea to chase every bolt hole. When a thread chaser is outside of your budget, use Grade 8 bolts and other fasteners with WD-40 to chase the threads. This may sound crude, but it will save you money and get the job done.
Engine stands are one of those purchase/rent questions because renting can sometimes cost you more than simply buying. Harbor Freight Salvage has some of the best values going at $50 to $100 for a stand. If you’re building a heavy big block, don’t cut corners here. Invest in a four-legged engine stand for stability and safety. The low-buck $50 stand will not hold up under the weight of a 650-pound big block. You don’t even want to think about what happens when an engine stand fails — it’s sudden, noisy, and destructive.
The decision to rent or buy tools boils down to how often you will use the tool and how long you will need the tool during your engine build. Any time you’re going to need the tool longer than 1 - 3 days, you’re probably better off buying. If you have to buy, look on the bright side. You can always loan it to friends or sell it after your engine is finished. Keeping it makes it a useful piece of community property among friends.
KEEP A CLEAN SHOP
We cannot stress enough the importance of keeping a clean, organized shop. Do your engine teardown work where you can catalog everything and keep it in its rightful place. Keep engine parts and fasteners in jars or plastic containers that are labeled. Haul the block, heads, crankshaft, and connecting rods to a machine shop immediately upon disassembly. This avoids any confusion and keeps you rolling. If you cannot afford the machine shop at the time, leave the engine assembled until you are ready. We speak from experience on this one because too much is lost both mentally and physically once the engine is disassembled. Keep disassembling, cleaning, machine work, and assembly as cohesive as possible.
It is always a good idea to keep an engine project organized from planning to completion. Know what you’re going to do and when you’re going to do it. Then get busy and see your engine project through to completion. Nothing is more discouraging than a disassembled engine that’s going nowhere because you didn’t have a plan.
Making Power
There is plenty of folklore about making power, such as the myth that it’s easier to make power with a Chevrolet than with a Ford. Nonsense. The truth is, you can make just as much power with a Ford, for the same amount of money, that you can with a Chevrolet. There is no black magic here — just the simple physics of taking thermal expansion and turning it into rotary motion.
To learn how to make power with a given engine, we have to understand how power is made. How much power an engine makes depends on how much air and fuel we can pump through the engine, and on what we do with that fuel and air mixture during the split second it is in the combustion chambers.
We have to think of an internal combustion engine as an air pump. The more air and fuel we can pump through the cylinders, the more power we’re going to make. This is why racers use big carburetors, manifolds, heads, superchargers, turbochargers, and nitrous oxide. Racers understand this air pump theory and practice it with wreckless abandon, sometimes with catastrophic results. Good racers also understand the “too much of a good thing” theory. Sometimes it can cost you a race, and sometimes it can cost you an engine.
Getting power from our air pump takes getting liberal amounts of air and fuel into the chambers, then squeezing the mixture as hard as we can without damaging the engine. When we raise compression, we increase the power of our mixture yields. It is the intense heat of compression coupled with the ignition system spark that yields the energy from our mixture. The more compression we have, the greater the heat created to ignite the mixture.
However, when there’s too much compression and with the resulting heat, the air/fuel mixture can ignite prematurely resulting in preignition and detonation. So we have to achieve the right compression ratio to get the most from the fuel we have. Today’s street fuels won’t tolerate much over 10.5:1 compression. This means we have to look elsewhere for answers in the power equation, like more aggressive camshaft profiles, better heads, port work, hotter ignition systems, exhaust headers that breathe better, state-of-the-art intake manifolds and carburetors, even electronic-fuel injection where we never thought of using it before.
The thing to remember about gasoline engines is this: The fuel/air mixture does not explode in the combustion chambers, it “lights off” just like your gas furnace or water heater. Because the mixture is compressed and ignited, it lights off more rapidly. Combustion in a piston engine is just that, a quick fire that sends a flame front across the top of the piston. Under ideal circumstances, the flame front will travel smoothly across the piston dome, yielding heat and pressure that act on the piston and rod to yield rotary motion at the crankshaft. A bad “light off” that originates at two opposing points in the chamber is the preignition or detonation that we mentioned earlier. The opposing light offs collide creating a shock that hammers the piston dome which is the pinging or spark knock we hear under acceleration. The objective is to get a smooth, quick fire, with the flame front traveling in one, smooth direction for maximum power. Call this power management.
Power management is having the right balance of ignition timing, fuel mixture, compression ratio, valve timing events, and even external forces like blower boost or nitrous input. All of these elements have to work together if we’re to make productive power. Let’s talk about some of the elements we need to make power.
Nitrous oxide or “squeeze” is all the rave today for those looking for quick and easy power (50 to 150 horsepower) on demand. Nitrous makes boatloads of power at the touch of a button, but it can be very harmful to a budget engine that isn’t properly prepared. Nitrous will severely damage your pistons and rings if not properly executed. It can and does hammer rod bearings resulting in severe wear. It is also hard on main bearings due to these loads. No matter what the nitrous oxide optimist club will tell you about “laughing gas”, nitrous can and does shorten engine life. So don’t be drawn into believing it’s a magic horsepower pill without consequences. If you’re going to be using nitrous oxide, be prepared for its shortcomings. Accept the fact that nitrous will shorten engine life no matter how it is used. The more aggressively you use nitrous, the shorter your engine will live.
It is easy to be lulled into believing a larger carburetor, more aggressive camshaft, and large port heads will make more power but this isn’t always true, especially in budget street engines. Induction, camshaft, and heads should always jibe with your performance mission. What’s more, you want your engine to survive while making all that power. Your engine build plan needs to include a common sense approach that involves the right selection and packaging of parts for best results.
If you’re building a daily driver, you’re going to have to compromise to some degree in terms of performance if you want reliability. We compromise because radical engines don’t do well for the daily commute. They also struggle to pass a smog check, depending on where you live. Radical camshaft profiles give the engine a rough idle, which can be frustrating in traffic and make it virtually impossible to pass a smog check. Loud mufflers can cause hearing damage and make for an annoying drive. They can also get you a ticket for noise pollution in some communities. A high compression ratio can cause overheating when traffic comes to a stop. Overcarburetion fouls spark plugs and pollutes the air.
This brings us to another valid point -- air pollution. Environmentalists and performance enthusiasts don’t get along, but it is our responsibility as performance buffs to build and tune our engines for cleaner emissions and better human health. This doesn’t mean you have to go out and buy catalytic converters and a smog pump. It does mean you need to package your induction and ignition systems for optimum emissions performance at the tail pipe. In short, clean up your performance act.
Carburetors play a role in pollution, too. A big, fat 750 or 850cfm Holley carburetor looks good at the drag strip, cruising spot and car show, but it is not a practical carburetor for everyday street use where clean emissions are important. This isn’t so much about Holley carburetors as it is about carburetor sizing in general. We want carburetor size and engine mission to be compatible for optimum performance and cleaner emissions.
If you think this clean emissions hoopla is a lot of nonsense, consider the last time you were behind a hopped up vintage musclecar in traffic that made your eyes water. Also remember that if your vehicle falls under the guidelines of state emission laws and smog checks, the law doesn’t give you a choice. Clean up your exhaust emissions or face revocation of your license plates in some states.
Building an environmentally responsible engine doesn’t have to be difficult either. Carbureted engines are not going to burn as clean as fuel-injected versions. If you can run electronic fuel injection, do so for cleaner air. Do so for your own health and for the sake of others who breathe. If you can’t, be conservative in your performance plan and dial in the right size carburetor.
Instead of a 750 or 850cfm carburetor, opt for a 600 or 650cfm carb and see how your engine performs. A carburetor that’s too small will become apparent quickly in the absence of torque as RPMs increase. Large carburetors give us more torque on the high end. Smaller carburetors do well on the low end. Choosing the right amount of carburetion is often trial and error.
Keep proper carburetor jetting in mind, too. Jets that are too large will make the engine run rich or “fat”, burning the eyes of those who have to follow you. Jets that are too small can be harmful if you’re leaning on it hard and lean detonation burns a hole in a piston. Again, fine tune carburetor and jet sizing for best results. Always err on the side of rich versus lean for longer engine life. If you really want to make a lasting impression on the community, go for a smog check each time you make a carb/jet change and see what it does for emissions. Cleaner air is up to all of us.
PLAN FOR POWER
The important question is, how much power do you want your engine to make and what can you afford? We’re assuming you have invested wisely in your engine’s bottom end with healthy parts and building procedures that will make the most of the engine’s potential. For example, if your plan is 450 to 500 horsepower from a small block, stock rods and cast pistons won’t cut it. Ask yourself what your engine’s bottom end can withstand, and then program the power accordingly. If you are seeking 450 horsepower, then hopefully you have prepared the bottom end with heavy-duty rods and pistons, coupled with building techniques to ensure that your engine survives.
Making power in a Ford engine has everything to do with air flow. A popular misconception suggests that the larger the carburetor, intake, and cylinder head ports, the more power you are going to make. In part, this is true. However, you must ask, where do you want the engine to make power and why? If you are building a drag or circle-track racer, you are going to want the engine to behave differently than you would a street engine. Racing engines make their power in a much higher RPM range than a street engine. A circle-track racing engine is going to make power differently than a drag-racing engine. Torque needs to come on strong from part throttle to full throttle with a circle-track engine. Drag-racing engines need to make torque at high revs. In either case, we have to design an engine that delivers power when it’s needed or the whole thing is pointless.
[attachment=1936]
Have you invested in a strong bottom end? Before you can make real power, you should have a bottom end that can handle the power. All that power is useless if you have a soft bottom end. Failure should never be an option.
A good street engine should make excellent low-end torque, yet be snappy when it’s time to wind it tight. With that in mind, which carb, manifold, cylinder heads, and camshaft should you choose? First, you’re going to want cylinder heads that are compatible with your pistons. With flat-top pistons (which most street engines should have), the field is wide open. If you’re opting for stock cylinder heads, keep combustion chamber size and deck thickness in mind. Nothing beats older Ford cylinder heads for compression, thanks to smaller chambers. An early 289/302 small-block cylinder head with 57cc chambers, coupled with flat-top pistons, will yield a compression ratio of approximately 10.0:1 depending upon compression height. Late-model 302 heads with 64cc chambers will yield less compression, which may mandate shaving the block and head deck surfaces to achieve the 10.0:1 ratio desired. Keep this in mind when shopping cylinder heads.
[attachment=1937]
Making power has everything to do with airflow. Where do you want your engine to make power? Where will your engine’s power band be most of the time? Large ports, such as those found in this 351C-4V head, have little value in daily street use. Huge ports do their best work at high RPM, where we need lots of airflow. For low-end torque, we need smaller ports where air velocity increases at lower revs, giving us all-important torque where we need it most.
Cylinder Block
The foundation for an engine build is the cylinder block. Whether it’s a small or big block, selecting the proper block for your build is the single greatest decision you will make aside from choosing the right machine shop. Depending on the block you need, selecting the right one can often be a great challenge. For example, a four-bolt main Boss 302 block will be a lot tougher to find than a garden-variety 302 block. Likewise, a 427 cross bolt will be more of a challenge to locate than a 390 block. In this section, we’re going to show you how to choose a block. We’re also going to show you how to tear down, inspect, and build one.
When you’re shopping for a block, close inspection is vital. The cylinder bores should be sized before you go any further. Small-block Fords should never be bored beyond .040-in. oversize. Some builders have gone to .060-in. oversize, but this is not recommended. If a block is already at .030-in. oversize, you may have .010 in. more to play with. If bore taper is greater than an .011-in. variance, find another block because the only overbore choice then is .060-in. oversize. Three exceptions to the small-block overbore limit are the 351C, 351M, and 400M. These blocks can be bored to .060-in. oversize if they have already been bored .030-in. or .040-in. Big blocks, with the exception being the FE-series 427, can be bored to .060" oversize. The 427’s limit is .030" oversize, and this is marginal.
While you’re shopping for blocks, we suggest having the block sonic tested for cracking and other irregularities. Sonic testing finds irregularities in the casting the human eye cannot see. Some Ford blocks, such as the 351C, 351M, and 400M, are notorious for cracking. Cracking is hard to see even with an antiseptic casting. Sonic testing can be expensive, but it beats the costly mistake of cleaning and machining a block only to discover it is cracked later.
[attachment=1938]
[attachment=1939]
Your initial block inspection should reveal obvious defects like cracks, damaged threads, damage to the cast iron or aluminum, scratched or gouged lifter and cylinder bores, flawed decks, welds in the casting, chipped or broken cylinder skirts, etc. Close inspection is important before working your plan.
Some block cracking can be repaired via welding or JB Weld. JB Weld is a two-part catalyzed product that works well with cracked cast iron. Properly mixed and cured, it will last the life of any engine block. For JB Weld to work effectively, you need a clean surface and a crack that has been carefully stop drilled at each end. Just a small 1/16-inch stop drill hole at each end slows and stops cracking. Then weld or JB Weld the crack. We suggest against the use of JB Weld on the cylinder walls and decks where stresses can be extreme. Your machine shop will know best on what call to make on repair. Some blocks are cracked beyond repair.
When you’re putting together a good formula for a block, sometimes you have to opt for different main caps for a stronger build. For example, you can take the main bearing caps from a 289 High Performance block that is beyond salvage and use them on a standard 289/302 block. You can also use main bearing caps from a Mexican block 289/302 for the same purpose because they’re wider and heavier. Along this same thought is the 351C block. You can convert a 351C two-bolt main block to four-bolt mains so long as you have four-bolt main caps from a trashed four-bolt main block. We do this by drilling and tapping the two-bolt main block for four-bolt mains. In the raw, the two-bolt and four-bolt main 351C blocks are basically the same casting.
Main bearing saddle trueness is another important issue facing the budget engine builder. The alignment of the main bearing saddles is rarely a cause for concern during an engine rebuild. Align boring and honing the main bearing saddles can be expensive. But it’s sound judgment. It would be wise for you to have a machine shop check the line bore for proper alignment before going any further. If the block needs to be align bored and honed, it is well worth the cost in terms of increased engine life because it gives the crankshaft a true foundation. Distorted main bearing saddle alignment puts undue stress on the crankshaft, which directly affects wear and tear. The stressed crankshaft alters connecting rod side clearances and puts stress on the main bearings. This can result in shortened engine life due to abnormal wear patterns.
With bore size and line bore out of the way, it is a good idea to check the block for cracks, obstructed water jackets and oil galleries, and other problems. Like we said earlier, cracking is something you don’t want to find after the machine work is finished or the engine is assembled. Finding it early in the game is crucial. Magnafluxing and sonic testing are two means of checking for cracks. Magnafluxing is a simple test easily accomplished by a machine shop. We set up a magnetic field around the suspected area using an electromagnet, then we sprinkle iron powder over the area. Iron particles will collect at the crack, making it easy to see.
Spot checking is yet another means of crack detection. With spot checking, we use a dye and a powder developer to “spot check” cracks. The nice thing about spot checking is the ability to use it on aluminum castings as well as iron. Magnafluxing cannot be used on aluminum castings.
The most common cracking areas are block decks and main bearing webs because these areas are subject to high stress. Check these areas closely and take your time. Block decks become stressed from cylinder head bolt torque plus the high heat and pressure that take place in this area. Main bearing webs are also placed under great stress from bolt/stud torque, plus the horrific loads this area experiences. Use every means available to ensure you’ve found a solid block.
Obstructed coolant passages have created more than their share of headaches for engine builders. Mass engine rebuilders are sometimes guilty of knocking old freeze plugs into the water jackets to speed disassembly. Unfortunately, whoever gets this engine after the fact must deal with overheating issues because those freeze plugs knocked into the jacket obstruct coolant flow and heat dissipation. During disassembly, take a bright light and inspect cooling passages (water jackets) for any obstructions and corrosion. Passages between the heads and block sometimes become clogged with rust and iron particles. Make sure these passages are clear.
Oil galleries can become clogged with sludge, metal particles, and nylon, which starves important moving parts of oil. We mention “nylon” because failed timing sets shed nylon and aluminum particles into the oil pan clogging the pick-up and oil galleries. What’s more, these particles find their way to the main, rod, and cam bearings causing excessive journal wear and engine failure. This is why close inspection of oil galleries is vital to any engine build. You’re going to need a long wire brush, solvent, and water under pressure to ensure all passages are sanitary. If this seems excessive, consider the cost of engine failure and having to do this all over again.
Another area we rarely see addressed is lifter bores, but lifter bore side clearances are vital to oil control and proper lifter function. Lifter bores should be inspected for scratches and nicks, then honed as necessary. Engines that have been sitting for a long time often experience ceased lifters that become welded to the bores. We suggest extreme caution removing the lifters because you can permanently damage the bores. Then inspect the lifter bore for scoring, nicks, and other damage. Ceased lifters can be worked loose with WD-40 (a good soaking) and a pair of vice grips. Lifter bore side clearances should be checked using a new lifter as a reference. Side clearances should be 0.0005 to 0.0020". You may also use a small dial-bore gauge or micrometer to check lifter bore size. Check the bore diameter, then lifter diameter to determine clearance. Remember, all lifter bores should be checked because all wear differently.
BLOCK & CASTING IDENTIFICATION
Ford makes it easy for enthusiasts to identify corporate castings. Please understand that Ford casting numbers aren’t always the same as part or engineering numbers. Identifying a casting is a matter of knowing what Ford part and casting numbers mean. Here’s what you can expect to see.
It’s easy to identify Ford castings once you understand the system because there’s not only a casting number, but a casting date code that tells you exactly when the piece was cast. Not only that, a date code is stamped in the piece which tells the date of manufacture. With these two date codes, we know when the piece was cast and when it was ultimately manufactured.
Ford part numbers can be found in the Ford Master Parts Catalog on microfilm at your Ford dealer or in one of those 900-pound parts catalogs from the good old days. Because Ford has discontinued a great many parts for vintage Fords, these part numbers don’t always exist in present day dealer micro films. This is called “NR” or “not replaced” which means it isn’t available from Ford any longer. However, casting numbers on parts tell us a lot about the piece.
DATE CODES
Date codes can be found two ways in Ford castings. When the four-character date code is cast into the piece, this indicates when the piece was cast at the foundry. When it is stamped into the piece, this indicates the date of manufacture.
Another area of interest to Ford buffs is where the piece was cast or forged. With Ford engines, we’ve seen three foundry identification marks. A “C” circled around an “F” indicates the Cleveland Iron Foundry. “DIF” indicates Dearborn Iron Foundry. “WF” or “WIF” indicates Windsor Iron Foundry. Single and double-digit numbers typically indicate cavity numbers in the mold.
Rotating Assembly
What we build into an engine’s bottom end directly determines durability and lifespan. Believe it or not, you can build integrity into a budget engine if you understand what counts and where to prioritize. Your focus needs to be on areas that do count. This means using the best parts available in your budget range; in short, spending money where it makes the most sense in a budget engine build.
When we’re planning a budget engine, it is wise to plan for the best our budget can buy, then cost down as necessary, prioritizing as we go. For example, you might want a set of Crower Sportsman rods topped with forged pistons. When cost enters the picture, you may have to throttle back to hypereutectic pistons and modified stock rods to get the job done. Compromising down under is something you do carefully, answering yourself honestly what this engine is going to be.
Before you get started, it is important to remember there are no guarantees when we build an engine. Anytime we build an engine, we always run the risk of engine failure due to flawed materials or faulty assembly procedures employed during the build. Additionally, there is the risk of engine failure due to abuse once in service — such as over-revving, poor tuning, or the neglect of proper maintenance like regular oil changes. The best we can do is to put quality into an engine build in the first place, then do our best to treat the mill respectfully once the chambers are warm.
Treating the mill respectfully means using common sense. Never push a cold engine, for example. Cold oil doesn’t flow and coat moving parts as liberally as warm oil. Cold parts need warm-up time to expand to proper tolerances. Operating an engine in a poor state of tune is another factor. Too much timing or a lean fuel mixture is hard on an engine. Too much of either will destroy an otherwise healthy engine in seconds.
FIRST, A WORD ON BALANCING
Before we get into how to build a solid bottom end, we must first talk about
balancing issues and how they pertain to Ford V-8 engines. Proper dynamic balancing is rooted in having the right combination of rotating and reciprocating parts. All Ford small-block engines, including the 351C, 351M, and 400M, are “externally” balanced. This means we counterweight the engine “externally” on the flywheel/flexplate and harmonic balancer to achieve dynamic balance.
Why go outside and externally balance? Because the crankshaft counterweights inside don’t always give us sufficient weight to counter reciprocating bobweight (rods and pistons). We add counterweight to the flywheel and harmonic balancer to make up for the difference in reciprocating weight inside the block. Look at a small-block Ford flywheel, flexplate, and harmonic balancer and you can see the counterweighting. On flexplates, the counterweight is welded on. With flywheels, it’s an integral part of the casting. Holes are drilled in the flywheel, often opposite the counterweight, to achieve ideal dynamic balancing. The same can be said for the harmonic balancer, which is also drilled to achieve ideal dynamic balance. We drill flywheels and harmonic balancers to remove weight where it isn’t needed.
One Ford small block, the 1963-67 289 High Performance V-8, uses additional counterweighting (a slide-on counterweight) at the front of the crankshaft to allow for heavier reciprocating weight inside. If you’re building a replica Hi-Po, you don’t have to have this counterweight. Your machine shop can fill the crankshaft counterweights with Mallory metal or add weight to the flywheel/flexplate.
Why is all this balancing hoopla important? Whenever we’re dynamic balancing an externally balanced engine, we must have the flywheel (manual transmission), flexplate (automatic transmission), and harmonic balancer present at the time of balancing. Horrible vibrations abound when we ignore this fact.
What makes the small-block “external” balance issue more complicated is 28-ounce offset balance versus 50-ounce offset. Earlier Ford small blocks like the 221, 260, 289, and 302 V-8s through 1981 were 28-ounce offset balanced. When Ford began producing the 5.0L (302) High Output V-8 in 1982, a 50-ounce offset balance was used to allow for heavier reciprocating masses inside. Small-block crankshaft flanges are drilled to allow flexplate or flywheel installation one way only. This prevents us from incorrectly installing the flywheel or flexplate, adversely affecting balance.
Ford FE big-blocks were both internally and externally balanced depending on engine type. All FE engines, except the 410 and 428, were internally balanced. Internally balanced means the crank, rods, and pistons are balanced together without concern for the flywheel, flexplate, or harmonic balancer. Internal balancing means there’s enough counterweighting in the crankshaft counterweights to do the job without help from the flywheel, flexplate, or harmonic balancer.
The 410 and 428 were externally balanced because they had greater reciprocating weight than other FE counterparts. Both had heavier rods and pistons, which made it necessary to add counterweighting outside the engine at the flywheel, flexplate, and harmonic balancer. The 428 Cobra Jet has an additional slip-on counterweight at the front of the crankshaft behind the harmonic balancer to allow for heavier moving parts inside.
We’ll take the FE story a step further with the FT (Ford Truck) big-block cousin. If you’re using a cast or steel-forged FT truck crankshaft (affordable brute strength) in your FE engine, always remember FT engines are externally balanced which means the flywheel, flexplate, and harmonic balancer must be included in the balancing process.
All 385-series 429 and 460ci engines are “internally” balanced, which means they don’t need any help outside at the flywheel, flexplate, or harmonic balancer. This is a big plus for the 385 because it makes dynamic balancing easy. When it’s time to replace a clutch and flywheel, you can expect a good balancing experience because the crankshaft, rods, and pistons are independent from the flywheel, flexplate, and harmonic balancer.
STROKER KITS
Pumping up the displacement in your Ford V-8 doesn’t have to be expensive. In fact, when you opt for a cast crankshaft and cast pistons, stroking your budget engine doesn’t have to cost any more than a simple rebuild. Stroker kits are available from Performance Automotive Warehouse (PAW) for not much more than a budget engine kit. Ditto for Summit Racing Equipment and Ford Racing Technology.
An engine is stroked by increasing the distance the piston travels in the cylinder bore. When we increase the distance the piston travels in the bore, the bore takes on more air and fuel resulting in more power. Stroker kits vary in scope and cost. Often you can stroke an engine without buying a kit using off-the-shelf parts. For example, you can stroke a 390 to 410+ci by installing a 428 crankshaft, or turn a 429 into a 460 with a 460 crankshaft. Just offset grind a 302 or 351 crank and use the right rod and piston for increased displacement from your small block.
Stroker kits are the easiest means to displacement when off-the-shelf Ford parts won’t get you there. Ford Racing, for example, offers a 347ci stroker kit (M-6013-B347) for 289/302 blocks. This kit sports a nodular-iron 3.40" stroke crankshaft, KB flattop pistons, Federal Mogul high-performance connecting rods, and Grant piston rings. You must provide all machine work and dynamic balancing. Remember, this is an externally-balanced engine. Flywheel, flexplate, and harmonic balancer must be present for balancing.
Ford Racing also offers a 514ci stroker kit (M-6013-A514) for 429/460 big blocks. This kit includes a nodular-iron crankshaft with 4.30" stroke, M-6200-A514 connecting rods, choice of TRW forged pistons, Speed Pro piston rings, and Federal Mogul bearings. Like the small-block stroker kit mentioned earlier, this kit requires externally balancing with flywheel, flexplate, and harmonic balancer present.
Stroker engines are also available from Ford Racing. You can install 600 horsepower in a weekend with the M-6007-B514 crate 514ci big-block package. This engine has been dyno tested at 600 horsepower at 6,250 rpm, which is 590 ft./lbs. of torque at 4,750 rpm.
Coast High Performance has a variety of stroker kits for Ford V-8s. The most popular is the 347ci Street Fighter small block. Several versions with either I-beam or H-beam rods are available for your application depending on budget. Coast also offers 377, 408, and 426ci stroker kits for 351W and 351C engines. If you’re building a 385-series big block, Coast can help with 501, 514, and 557ci stroker kits for your monster big block.
Keep in mind that when you’re ordering a stroker kit for your Ford V-8, the more expensive kits sport H-beam rods, forged pistons, and steel cranks. Rules of budgetary concern must apply here. Street engines don’t need race-ready pieces. Keep your expectations realistic and an eye on the check book.
Cylinder Heads
You can achieve significant gains in engine power with the proper selection and modification of cylinder heads. Cylinder head port size and shape, coupled with combustion chamber size and shape, determine an engine’s power personality. The “bigger is better” theory most of us have accepted over the years doesn’t always work to an engine’s advantage. A street engine can have too much cylinder head, which adversely affects driveability. The same can be said for racing engines, depending upon the application. Ports that are too large hurt the low-end torque we need for effective street performance. Your challenge is to achieve the right combination of port size and camshaft profile to enhance driving pleasure. You’re going to want a cylinder head/piston/induction/camshaft combination that will serve you well in regular driving as well as traffic light-to-traffic light performance.
How you intend to use the engine directly determines the type of cylinder head you should select. Budget street engines benefit more from the smaller ports we see with stock heads. They don’t always need porting and polishing, either. Sometimes porting and polishing take street power away from where you need it most. Stock intake ports that are rough cast keep fuel droplets in suspension on carburetor equipped engines. This improves low-end torque. Ground and polished intake ports can actually hurt low-end torque on carbureted engines because fuel atomization and suspension are affected.
SMALL BLOCK
One of the biggest myths you will face in your Ford engine build is that the 289 High Performance head is the best head to use. This is not necessarily so. The only difference between the 289 High Performance head and the 2V/4V head is valve spring pockets and screw-in rocker-arm studs. Otherwise, port size is virtually the same. So save your money and spruce up a set of 2V/4V heads or opt for 351W types. How? By doing some port work, opting for screw-in rocker-arm studs, and installing hardened valve seats and larger valves.
If you’re building a 289 High Performance engine, opt for larger 1.94/1.60" Chevrolet valves (no one’s going to know they’re there but you) and a port/bowl job to achieve the most from those factory Hi-Po heads. Externally, they will look stock. Internally, they will help your 289 High Performance engine breathe like it never has before. You can also opt for 351W heads here too without anyone knowing the difference externally.
Vintage small-block Ford head choices aren’t as simple as they may appear. There has been significant change in the 221/260/289/302 head over the past four decades. Some of these heads are best avoided. Others are diamonds in the rough.
The best small-block head to use is the 1969-73 351W, thanks to its larger valves and ports. It’s a bolt-on swap. When a 351W head cannot be sourced, the 1965-73 289/302 head is your best bet, due to its smaller wedge chambers. We stress head use prior to 1974 because combustion chamber size remains smaller in those years, keeping compression healthy.
When you are building a set of heads, good machining technique is important. First, castings should be checked for cracks and serious warpage. Then head deck surfaces should be checked and milled as necessary. Valves and guides should be reworked or replaced. Hardened exhaust valve seats should be installed. Pushrod guide plates and screw-in rocker-arm studs should be fitted. When budget is limited, you should opt for 1965 through early 1966 heads with pushrod guides already cast. If you are running a hot camshaft, screw-in rocker-arm studs become mandatory. When screw-in studs are beyond your budget, pinning the press-in studs becomes an inexpensive alternative.
Bush Performance in Fort Smith, Arkansas offers a low-cost way to get into hot street performance with the Street Boss system (nicknamed the “Clevor”, for Cleveland and Windsor). The Street Boss system puts the 351C head atop the 289/302/351W block. The way you intend to use your engine determines which 351C head you will use. For the weekend racer, the 351C-4V head with its large ports and closed-wedge chambers makes a good high-rev head. The 351C-4V head breathes very well at high RPM like we see in drag and road-course racing. The 351C-2V head is a better street head due to its smaller ports and open-chamber design. Smaller ports give you better low-end torque. Open chambers reduce the risk of detonation with low-octane fuels.
[attachment=1940]
The 1969-73 351W head is a budget performance bolt-on for 289/302ci engines due to its larger valves and ports. The only important difference to watch for is the dog-leg coolant passage between the intake manifold and cylinder head on early 351W heads. This can pose leak problems if you use the wrong intake gasket. Use the 351W intake manifold gasket.
New aftermarket heads aren’t within the realm of a budget build. However, as they age and see use, they often wind up at the swap meets for considerably less than they were new. Glass beading and valve work makes them as good as new for less money. Good street heads include the Ford Motorsport SVO GT-40 iron and aluminum heads, World Products Windsor Jr. heads, and Edelbrock Performers. These are the most common, most reliable heads out there for the builder on a budget.
For those of you building late-model 5.0L and 5.8L engines, cylinder head choices tend to be different, especially if you’re interested in meeting emission standards. From 1982-84, Ford used a D9AE-6049-AA cylinder head casting atop the 5.0L High Output V-8. This is not a high-performance cylinder head although it was used on the 1982-84 5.0L High Output engines. It is, however, a workable cylinder head that will come alive with port work and larger 1.94/1.60" Chevrolet valves.
Small-block Ford heads lost yardage in the performance arena after 1978 with Ford’s increasing attention to emissions and driveability. Ports became smaller for improved low-end torque and cleaner emissions. Although this works well in traffic, it doesn’t do much for our engine in higher RPM ranges. Despite the D9AE casting shortcomings, you can still port these heads and make power. However, this is not maximizing what you can do with a stock cylinder head.
The biggest shortcoming with the D9AE casting is the exhaust port with Ford’s infamous Thermactor injection “hump” in the port. It becomes very restrictive. However, this hump can be ground out and all restriction taken away with some Saturday afternoon labor on a work bench. For 1985 only, Ford went to the E5AE head, which was little more than a modified D9AE casting designed for easy roller tappet removal with the head installed. It is identifiable by the reliefs notched in the head at the lifter valley. Otherwise, it is virtually identical to the D9AE casting.
Ford began making improvements to the 5.0L/5.8L head in 1986 with the “high-swirl/fast burn” E6AE and E6TE castings. This head saw widespread use from 1986-88 depending on vehicle application. A shrouded intake valve was trademark to the “high-swirl/fast burn” concept. Thing is, the E6AE/E6TE head didn’t do much for power.
The E5TE and E7TE heads introduced for 1987 are undoubtedly the best late-model castings because the “high-swirl/fast burn” chamber is eliminated. This is more a return to the 1985 High Output/Truck head with improved water jacket passages. For you the engine builder, this head is good for an easy bonus 25-30 horsepower.
The 1993-95 Cobra GT-40 head is little more than a marine head with larger valves and ports. This fact all by itself makes the GT-40 a good, economical head for 5.0L/5.8L performance. Economical because it is a common head. Just look for 1.84/1.54" valves, “GT” markings, and F3ZE/F4ZE casting numbers. Ford part numbers are F3ZZ-A and F4ZZ-A. These heads are also available from Ford Racing as M-6049-L302. Properly outfitted, these heads use the F3ZZ-6564-A roller rocker arm with a 1.7:1 ratio.
Camshaft and Valvetrain
The camshaft and valvetrain directly determine not only an engine’s personality, but how reliably it will perform throughout its service life. Unfortunately, a lot of folks have more misconceptions about camshafts than they have facts. Hopefully, in the following pages we can set you straight on the myths and get you headed in the right direction.
To understand how to pick a camshaft and valvetrain, you must first understand how it all works. Choosing a camshaft profile must be based on how you want an engine to perform. Are you building a streetable engine where low- and mid-range torque are important? Or are you building a high-performance racing engine that makes peak torque in the high revs? Whatever the application, it is vital for you to choose the right combination of components.
A camshaft manufacturer’s catalog lists dozens of camshaft types for the same type of engine. This is where it gets mighty confusing for the novice. We see words like lift, duration, lobe separation, base circle, lobe centerline angle, and valve overlap. What does all of this information mean and how will it affect your engine’s performance?
CAMSHAFT SHOP TALK
What makes one camshaft different from another? Call it profile. Profile refers to the lobe’s design, dimension, and positioning, as well as its functionality. Functionality refers to when the lobe opens the valve, when it closes the valve, how long it keeps the valve open, and how much it opens the valve. All of these factors influence an engine’s performance.
Following are a few terms that you will hear in the shop when talk turns to camshafts. Lift is the maximum amount a lobe will open a valve. Duration refers to how long the lobe will keep the valve open. Lobe Separation or center line is the time or duration between intake and exhaust valve action. Overlap plays into lobe separation because it is the period when the exhaust valve is closing and the intake valve is opening. The Ramp is the ascending or descending side of the cam lobe coming off the base circle when lift begins to occur. The Flank is the ascending or descending portion of the lobe past the base circle nearest maximum lift. The camshaft’s Base Circle is the portion of the lobe that doesn’t generate lift. The bottom-most portion of the lobe is called the Heel.
Flat-tappet camshafts work differently than roller-tappet camshafts, which means you have to think differently with each type. Flat-tappet camshafts limit what you can do with lobe profile
if you want street-ability. If you want an aggressive profile with flat tappets, you can only go so far with a street engine or suffer with poor drive-ability (rough idle, low manifold vacuum). If
you want an aggressive profile in a street engine, we suggest stepping up to a roller camshaft, which can handle the aggressive profile better using roller tappets.
STREET CAM FACTS
Based on everything we have seen in nearly 30 years of experience, the best street performance cams are ground with a lobe separation between 108 to 114 degrees. When you keep lobe separation around 112 degrees, you improve drive-ability because the engine idles smoother and makes better low-end torque. This is what you want from a street engine. Any time lobe separation is below 108 degrees, idle quality and streetability suffer. However, there is more to it than just lobe separation.
Compression and cam timing must be considered together because one always affects the other. Valve timing events directly affect cylinder pressure. Long intake valve duration reduces cylinder pressure. Shorter duration increases cylinder pressure. Too much cylinder pressure can cause detonation (pinging). Too little and you lose torque. You can count on cam manufacturers to figure stock compression ratios into their camshaft selection tables, which makes choosing a camshaft easier than it has ever been. Plug your application into the equation and you will be pleased with the results most of the time.
The greatest advice we can offer the layman is to be conservative with your cam specs if you want reliability and an engine that will live a long time. Stay with a conservative lift profile (under .500-in. lift). A high-lift camshaft will beat the daylights out of a valvetrain, and will put valve-to-piston clearances at risk. Watch duration and lobe separation closely, which will help you be more effective in camshaft selection. Instead of opening the valve more (lift), we want to open it longer (duration) and in better efficiency with piston timing (overlap or lobe separation).
Always bear in mind what you are going to have for induction, heads, and exhaust. The savvy engine builder understands that in order to work effectively, an engine must have matched components. Cam, valvetrain, heads, intake manifold, and exhaust system must all work as a team. If you are opting for stock heads, your cam profile doesn’t need to be aggressive. Select a cam profile that will give you good low- and mid-range torque. Torque doesn’t do you any good on the street when it happens at 6500 rpm. Choose a cam profile that will make good torque between 2500 and 4500 rpm. Otherwise, you are just wasting engine.
The thing to remember with camshaft selection is how the cam will work with your engine’s cylinder heads. We need to take a close look at valve lift with a particular head and determine effect. Some camshafts will actually lose power with a given head because there’s too much lift or duration. This is why it is important to understand a given cylinder head before choosing a camshaft. You want to seek optimum with any cylinder head/camshaft combination. This means having to really do your homework before making a decision. Part of building a successful budget engine is doing a lot of the homework yourself because you cannot afford a wasteful experience.
What type of fuel do you intend to run in your engine? This also affects camshaft selection. We can actually raise compression if we’re running a mild camshaft profile or using a higher octane fuel. It all has to work together. Camshaft timing events must be directly tied to actually raise compression if we’re running a mild camshaft profile or using a higher octane fuel. It all has to work together. Camshaft timing events must be directly tied to compression ratio. The longer our duration, the lower the cylinder pressure and resulting compression. The shorter the duration, the less air we’re going to bring into the cylinder, which also affects compression. Our objective needs to be the highest compression without detonation, which will harm the engine. With this in mind, we want the most duration possible without compression extremes. Duration is what gives us torque as long as compression is sufficient.
Valve overlap, as we have stated earlier, is the period between exhaust stroke and intake stroke when both valves are slightly open. This occurs to improve exhaust scavenging by allowing the incoming intake charge to push remaining exhaust gasses out via the closing exhaust valve. Were the exhaust valve completely closed, we wouldn’t get scavenging. The greater the overlap in a street engine, the less torque the engine will make down low where we need it most. This is why we want less valve overlap in a street engine and more in a racing engine, which will make its torque at high RPM. Increased valve overlap works best at high RPM.
Street engines need 10 to 55 degrees of valve overlap to be effective torque powerhouses. When valve overlap starts wandering above 55 degrees, torque on the low end begins to go away. A really hot street engine will need greater than 55 degrees of valve overlap, but not much greater. To give you an idea of what we’re talking about, racing engines need 70 to 115 degrees of valve overlap.
[attachment=1941]
Camshaft design can be confusing. Think of the cam lobe in geographical regions as it travels against the lifter: opening ramp, opening flank, nose, closing flank, closing ramp, then the heel. The base circle is the part of the lobe that doesn’t generate lift.
For a street engine, we want valve overlap to maximize torque, which means a conservative approach in the first place. Push overlap as far as you can without compromising torque. We also have to figure in lift and duration with valve overlap to see the complete power picture.
Lobe separation angle is another area of consideration in street cam selection. This camshaft dynamic is chosen based on displacement and how the engine will be used. Rule of thumb is this. Consider lobe separation based on how much displacement and valving you’re going to be using. The smaller the valves, the tighter (fewer degrees) lobe separation should be. However, tighter lobe separation does adversely affect idle quality. This is why most camshaft manufacturers spec their cams with wider lobe separations than the custom grinders.
Duration in a street engine is likely the most important dynamic to consider in the selection process. We increase duration whenever less lift is desired. Why? Because we get air flow into the cylinder bore two ways: lift and duration. We can open the valve more and for less time to get air flow. Or, we can open the valve less and keep it open longer via duration to get air flow. Each way will have a different effect on performance. Duration is determined by how much cylinder head and displacement you have, and how the engine will be used. Excessive duration hurts low-end torque, which is what we need on the street. So we have to achieve a balance by maximizing duration without a loss in low-end torque. We do this by using the right heads with proper valve sizing. Large valves and ports don’t work well at all for street use. Mix in too much duration and you have a real slug at the traffic light.
[attachment=1942]
This is a flat-tappet camshaft. Notice the cam lobe profile (shape). It is more aggressive by nature even with a stock grind. Streetability suffers when lift and duration are increased, making the idle rough and eroding manifold vacuum.
So what does this tell us about duration? Plenty. We want greater duration whenever displacement and valve sizing go up. Increasing duration falls directly in line with torque peak and RPM range. This does not mean we necessarily gain any torque as RPM increases. It means our peak torque simply comes in at a higher RPM range. An example of this is if our engine is making 350 ft./lbs. of torque at 4500 rpm and we increase duration. We may well be making that same amount of torque at 5200 rpm. In short, increased duration does not always mean increased torque.
Compression has a direct effect on what our duration should be. When we’re running greater compression, we have to watch duration closely because it can drive cylinder pressures too high. Sometimes we curb compression and run greater duration depending on how we want to make power. When we have greater duration, our engine is going to make more power on the high end and less on the low end. This is why you must carefully consider duration when ordering a camshaft. Higher compression with a shorter duration helps the engine make torque down low where we need it most in a street engine. The thing to watch for with compression is detonation and overheating. Maximum street compression should be around 10.0:1.
Valve lift is an issue we must think about as it pertains to an engine’s needs. Small blocks generally need more valve lift than big blocks. As we increase lift, generally we increase torque. This is especially important at low- and mid-RPM ranges where it counts on the street. Low-end torque is harder to achieve with a small block because these engines generally sport short strokes and large bores. Your objective needs to be more torque with less RPM if you want your engine to live longer. Revs are what drain the life out of an engine more quickly.
To make good low-end torque with a small block, we need a camshaft that will offer a combination of effective lift and duration. As a rule, we want to run a longer intake duration to make the most of valve lift. We get valve lift via the camshaft to be sure. However, rocker arm ratio is the other half of the equation. The most common rocker arm ratio is 1.6:1, which means the rocker arm will give the valve 1.6 times the lift we have at the camlobe. When we step up to a 1.7:1 ratio rocker arm, valve lift becomes 1.7 times that which we find at the lobe.