351W overheating

[furray]

Any idea how far it was bored ? Any block that needs to go more than .040 I'd get sonic checked first. Just because a mfgr offers a .060 over piston doesn't mean the block will have enough material in it to get by.

[noroz]

I did a pressure test and it held pressure fine.

The engine was rebuilt 2 owners ago (about 4-5 years ago). The previous owner only put about 500 miles on it and said it always overheated on him. I'll check the freeze plugs. One of the rebuilders I talked to said it's possible some stuff got in there during the rebuild or they just might not have done a good job putting it back together.

You said the Previous owner said it always overheated and it may have started, maybe just after the rebuild, which might suggest that the heads may not have been retentioned after the build (if retorque gaskets were used) + the old radiator may not have been flushed just to add to its woes. Quite often after hot tanking blocks are pretty clean. so I would have that lower on the list for now, if you have been good with using only coolant.

Could also be not enough ring clearance right from the start.

[JTS71 Mach1]

After reading the prior posts. I noticed you never mentioned if it was a Cleveland or a Windsor? If it is a Cleveland, there are several articles regarding the early Cleveland engines and that they have 2 different thermostats. It would be nice if it was that simple. Here's hoping. Search this site there are several articles on this very problem. Hope this helps. JTS 71 Mach1

[ylwhrse]

You are correct in that timing needs to advance on acceleration. Hooking it up to manifold vaccum is incorrect, by doing this the distributor will see vaccum all the time and the distributor will be in an advance position all the time. the ported vaccum is the way to go. Ported means somewhat just that. That ported vaccum does not have vaccum until the throttle is tipped in or you accelerate, then vaccum is there and advances the timing if the vaccum advance is indeed working properly. Its easy to check just unhook the line from manifold vaccum and plug port with a cap or finger, start engine and hook up a timing light and watch the timing mark and rehook the line up to the manifold vaccum. You should see the timing advance if it is indeed working. No timing light, that's ok you should when doing the same thing hear an audible change in engine RPM's or if tach equipped you can see a change in RPM's as timing increases. That being said and maybe I didn't read far enough in the thread but 1-are you losing coolant or seem to be ? Is your exhaust very moist looking as in extra water vapor in the exhaust more than normal? 2- with the engine running and the radiator cap off ( take it off before you start it or before its hot so you don't get burned and have the radiator pressured up) and watch the coolant. Is their bubbles in it? Is it flowing or do you see any movement in the coolant? If you have excessive water vapor in the exhaust or lots of bubbles in the coolant that can be a sign of a head gasket that is blown or starting to go. Even if you are not losing coolant you can have a headgasket start to go and leak hot exhaust into the coolant-IE bubbling. There are others ways to test this but it requires special equipment. Are you sure the timing is correct? Incorrect timing can make the engine run hot. Is the carb jetted correctly ? A too lean condition can caude the engine to run hot. How new is the radiator? I have seen clogged cooling fins in the radiator cause severe cooling issues or even clogged AC condenser that wouldn't allow airflow through it to the radiator. There are antifreeze additives that will lower coolant temps by 10-20 degrees that will work and will help but you are right that it is just masking the problem. Does the fan clutch freewheel easily or have a slight drag to it when you spin it over? It shouldnt spin freely freewheeling like a wheel bearing it should have some drag. It seems to me since it overheats while driving that it is an airflow issue/timing issue / rich lean issue or all combined. The last thing I would be sure and check and is a notorious 351 Cleveland problem is getting the wrong thermostat. They take a special thermostat. They also have to have the brass plate or water restrictor in the block and if that is missing it will overheat I promise and you will spend a ton of money on that one before figuring it out if you do. But I think yours is a 351windsor. I also remember that if the engine was rebuilt recently that if memory serves me right you can put the head gaskets on backwords so that the water passages do not line up correctly with the head and block thus creating a overheating problem. If I can help in any way please feel free to message me. I hate heating problems. You should even at highway speeds be able to run down the road without a fan and your engine should stay cool. The fan is really meant for stop and go and town driving-IE slow speed operation. Hope this helps ,
YLWHRSE

[noroz]

Hi, Hope your getting to the bottom of your heating issue. I forgot to mention to maybe check your radiator hoses for over expansion, say for example an over exagerated top hose may give clues.
Also look at your overflow system and correct poundage on your radiator cap, small things but they add up. Heating problems on V8s are a pain in the a§§ Im sure youll get to the source.
Good luck.