Should quench be looked at with a pent roof 4 valve engine like a Neon? My Neon blew up and I'm building up another one. Forged pistons in the stock compression ratio are not available unless they are custom made, so I'm gonna use 10:5 and maybe a thicker head gasket to get down to around 10. Stock compression is 9:8 for 87 octane which is what I want to use.

Pent-roof cylinder heads and true Hemi heads are difficult beasts to get squish into. There needs to be a surface that comes within 0.040 or so of the piston at TDC. Look at the progression of the GIII Hemi head (not a true Hemi but who cares, it works). The first generation had the "wings" on each side of the combustion chamber. They slanted up into the chamber. No squish available. The latest version has those wing areas brought level with the rest of the cylinder head's deck surface. Now bring a piston up to TDC and there can be squish if the clearances are right. My Mercedes M110 Hemi has a true "part of a sphere" chamber and the low compression pistons were flattops. The European high compression pistons had a raised portion which had a part of a sphere surface to come close to the cylinder head. I have attached a couple of pictures. The top picture shows the dome better, from 6 o'clock to 9 o'clock.

The pent roof four valve combustion chamber when viewed from the top, looks like a square (chamber) sitting on top of a circle (cylinder). There isn't much room for squish. For that reason most pent roof chambers depend more on swirl and tumble to create mixture motion.

My response to your original question would be unless you see that the factory built squish into the engine to start with, head gasket thickness shouldn't matter.

R.