QUOTE(McMark @ Dec 5 2012, 06:38 PM)
If you add shims to only one cylinder your heads won't seat/seal correctly.
This presumes that the cylinder spigot registers are the same distance from the crankshaft centerline and that the cylinders are all exactly the same height.
Which is a nice presumption, and I agree that if they're not like that, they all need to go to a machine shop and be made like that.
But if for some reason you wound up with a cylinder top that was, for some reason, just a little bit shorter than its neighbor, and if that cylinder also had less deck height (which should be the case, but we are measurung and verifying everything...) then one might be temped to use a 'big enough' base gasket to _make_ them be the same height. That is - it's the tops that matter, the bottoms less so.
And for completeness, we'll mention that you only get that complete perfect seal if the cylinder head mating surfaces are _also_ in exactly the same plane. There are those that claim they can be lapped to this standard, but I'm skeptical, and without putting words into the Capt'n's mouth, he's already on record as being skeptical as well...