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Posted by Chriscase [76.201.18.217] on Thursday, October 22, 2009 at 09:33:37 :
In Reply to: Low compression update posted by Glen Idaho [64.126.155.197] on Wednesday, October 21, 2009 at 22:33:30 :
I doubt that the wrong head can make that big of a compression drop. Maybe wrong pistons, like 230 pistons with a 218 crank? Or are the pistons the same and it's the rods that are different? But would the compression be lots lower? Did the pistons come all the way to the top of the block? Perhaps you can check through the little plug over #6? It looks like a bolt head, but goes in to the cylinder, and is right over the piston.
Or cam timing is a tooth off. To check, remove the fender liner, and the front valve cover. Turn engine over by hand until the exhaust of #1 closes, and the intake just opens. You want to "split the over lap", get it to where both valve are just slightly off their seats. Or maybe just slightly NOT off their seats. Maybe need a feeler gauge just a couple thou thinner than the settings? Anyways, splitting the overlap ought to happen when the timing pointer is at 0°. +/- a couple. If you are off by 10° or more, the timing chain was put on wrong. Do it a couple times to make sure before tearing into it.
On many engines, the gear marks don't line up exactly. So try moving it a tooth, and it ought to be WAAAY off, move it back.
Splitting the overlap is easier when assembling a V8, just put a straight edge across the top of the lifters. I used to do it on all the engines I assembled, to be able to fix retarded cams in smog motors. On many I would chamfer the back of the crank gear so I could put it on backwards, that timed the cam just right.
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