Motor help

[Osprey351]

New to this site name is Dan
Just bought a 70 mach 1 351 Cleavland 4v with 11to1 compression and i dont think thats going to work with pump gas. Im rebuilding the motor. So i can change some things if needed . But also want to get a little hp out of it .car is all original it seems but needs lots of work. But price was right . Also four speed car. Any advice would help. Thanks Dan

[Steven Harris]

Welcome Dan,

The best advice I can give on building your 351C 4V is to visit the Cleveland forum at: http://www.network54.com/Forum/119419/

They have a lot of experience with what works and what doesn't over there. You will be able to decrease your compression ratio and still up the horsepower by modernizing the 351C with modern cam technology.

Share some pictures of the car when you can.

[don29163]

my Q code 351C says....regular fuel and it runs fine on it...all stock.

[Klutch]

What's makes you think it has 11:1 compression? The original engine had, maybe, 10:1. I've heard from very reliable sources that the Cleveland engines were actually 1 full point lower in compression than advertised.

If someone built the engine with pop-up pistons then it probably has 11:1 compression. Flattop pistons would require a decked block and milled, closed-chambered heads to get a true 11:1 compression ratio.

Since you asked for advice for your build:

- The Blue Thunder is probably the best 4V intake. But they are somewhat expensive.

- The Edelbrock Performer and Performer Air Gap 4V are also good intakes. But you might have some clearance issues with the Air Gap. (The Air Gap will not work with a shaker unless you lower the engine or shave the shaker base.)

- Be very careful when choosing a cam for your Cleveland. A lot of cams have a grind best suited for a 350 Chevy; and this will not work well in a Cleveland. You might look into the Lunati Voodoo cams. They have a lot of grinds right off the shelf which are specifically designed for the Cleveland. If you go with a custom cam, again, be very careful. A lot of "experienced racers" will grind you a cam best suited for a Chevy. I've also heard a hydraulic version of the Boss 351 cam works very well on the street. So, you could use those numbers for a custom grind.

- A steep rear gear really helps a 4V Cleveland to get going. People who complain about a 4V Cleveland being a dog at low RPMs are running the wrong rear gear (and probably a cam profile for a Chevy).

- Think hard if you're considering a stroker kit. While it sounds way cool to have stump-pulling torque, it may not do you any good if you just light up the tires from a start.

- There are multiple schools of thought concerning oiling mods for the Cleveland. I've heard it's best to install lifter bore bushings, oil restrictors for the cam bearings and special pushrods with a small ID; all to improve oil flow to the bottom end instead of the top. I've also heard you can just install an oil bypass line from the front of the engine to the back and you're good to go. So what the real deal? I dunno. Let us know what you find out.

- You must absolutely, positively make sure you're not running the factory rod bolts or valves. The factory rod bolts are weak. Replace them. The factory valves were welded, two-piece units. If yours haven't already been replaced, replace them. Under no circumstances should you rebuild a Cleveland and keep the two-piece valves. All it takes is one valve failure to destroy your engine.

- Install a high quality, aftermarket harmonic balancer. The factory balancer was too small. The Boss 351 balancer was better, but even if you could find one, after all these years, it will be shot.

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