Madscientist needs to think outside the box.

Here's an example: The goal is to have 0.040" clearance between the piston top and the "squish" area of the closed chamber heads. If one adds all the numbers, it becomes obvious that with stock dimensions the high compression pistons end up sticking out of the block 0.018".

Now to get the desired clearance one needs a gasket with thickness 0.040" + 0.018" or 0.058". Send money to Cometic or scour the Fel-Pro catalogs, etc.

ANOTHER way to do it would be to mock up the block and measure how far the pistons actually stood out of the squared-off deck. The pistons would then be cut down the desired amount to get the surface of the "squish" area to zero deck. This would leave part of the piston still standing out of the deck.

The problem with buying the so-called "340 style" open chamber heads is that one is forever stuck with the squish area eliminated. Now if building a stroker engine, a custom piston shape is required to regain the mixture motion that the squish area would have supplied. On the other hand, the closed chamber head may require some material removal on the piston top to provide a desired compression ratio, but it is easier to remove material from a piston than to add it.

R.