This actually is related to a post I put on a few weeks ago about lifter problems & zero compression with a 351C, but I thought this would stand on its own. The other day I finally decided to tackle taking off the head that had ZERO compression both dry/wet tests. I didn't do a leak down test, I should've though. Well I was expecting to pull the head and see a burnt valve or destroyed valve seat, but Noooo, the head seems fine. I even shined a small mag-lite in the exhaust port at night and did not see a spec of light shining thru around the exh valve, also the intake was fine too. The head gasket looks like it is toast, maybe if blew!! Anyway now to my main idea on this post, when I went back to the motor & noticed I have a mixture of 2 different pistons in their bores. #5 & 6 cylinders are original flat top pistons, BUT #7 & 8 cylinders are dished pistons???!!! Yup you heard right folks! On the dished piston near the arrow pointed to the front of the engine is a stamped "ST", I'm assuming it is for standard measurement. The flat tops have no markings at all, just flat with the offset 2 valve reliefs. Now what would or was happening in that motor with different compression ratios going on??? It also has each intake valve replaced(no fomoco) in #7 & 8, but the #5 & #6 cylinders have fomoco on their intake valves. Who knows about the other head, but I didn't pull it cause it has decent compression ratios. I have another good used 351C standing by that runs decent which that's what I'm leaning on doing.
Sounds crazy but I've taken apart many engines to find the same thing. Finding mismatched heads is treat also I can understand if you live in a third world country and just need to get it running, but here in the good old USA it's not logical at all....
I've seen blocks with std, 20, 30 and 40 over all in the same block... From a local engine builder/machine shop...
We tore a 330 truck engine down for a mid engine noise, and a real low oil prsssure issue. Found six pistons the same, two were different, crank had been turned 030 on the mains, but had 020 bearings, and # 3 rod was bent
I've seen mixed pistons as well. Some people just don't want to or have the means to do things the way they should be done. At worst, you end up with an unbalanced engine with an unbalanced power pulse from the two low compression pistons. It'll run, it just won't run smoothly. There used to be a company that converted 302's into 4 cylinder air compressors, 4 cylinders ran it, the other 4 compressed the air into the tank.
These compressors had a special cam grind. The compressor worked off one head and the engine ran off the other head. Use to be an engine repair shop in the Atlanta area that also sold complete short or long blocks. They would turn what ever crankshaft journal needed turned and leave the rest...if a journal only needed .010 to clean up and the next journal needed .030 to cleanup then that’s what it got…same with cylinder walls. It was possible to get 3 or 4 different size bearings and different size pistons.
If tbis a $300 work car, I would run it till it crapped! I think a cleveland is worthy of a decent rebuild, someone patched this on shoestring budget for sure!
converted 302's into 4 cylinder air compressors, 4 cylinders ran it, the other 4 compressed the air into the tank. I had one of those, " Schramm " was the company. It was a damn good air compressor!
Just got back from the machine shop, they did a wet test on the head with #6 cylinder. The intake seat is worn & leaking very badly, they suggested a valve job for $300-all valves look good but the springs are bad. Also with with those 2 cylinders that have those dished pistons this motor will never be balanced or run decent-so to save bucks I'm just going to transplant another '70 351C I have that I know runs good!
