Deck Height

[Advokat]

Will probably get around to checking the deck height this weekend. I've never had to do this before so I was wondering if this is something that is done on all four cylinders or just on one? If just one, which do you choose?

If on all four, what do you do if the numbers vary? Use different sized barrel shims?

May seem like a goofy question, but I never did a rebuild other than stock before.

Thanks

[Marc]

All four for sure; you don't know if the crank is in the true center, if the case halves are machined identically, if the rods are the same length....
Be sure to clamp the barrels down firmly against the case, and check that a straightedge placed across them contacts at all 4 points - if one is "shorter" than its neighbor it'll need that much extra shim to come out even. A thousandth or two discrepancy is acceptable.
Measure along the centerline of the wristpin (not top & bottom where piston rock would make it inconsistent) - and if there's more than a couple thousandths difference between one end of the piston and the other you may have a bent rod or other problem.
You must keep both barrels on each side even so that the head can seal, so there may be some compromising to do.
It's of much less concern if one side needs more deck than the other to compensate for different combustion chamber volumes - even compression ratio matters more than identical quench volumes.

[danimal]

you should never be in a position where you have to run different sized shims under the barrels... if the deck height varies, you need to know exactly why.

one thing i always have done on all cases is to deck the case where the jug(or shim) sits on the case... i also run only machined, not stamped, shims.

the quality of stamped shims is much better than it used to be in the '80's, but it's still not worth it on a performance motor.


dan
oceanstreetvideo.com

[joe of centorg]

The line bore could be off center (from the case parting line), most are that I have checked.
Peace, Joe