340 Static Compression Numbers and Test Procedure

340inabbody said

Guys’s Never calculated the stack up but was wondering how much compression loss could be achieved with either thick head gaskets or “shims”. Is it on the order of a point or tenths of points?

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As a rule of thumb, you can count on approximately 0.1 point loss of compression ratio for every .005" increase in head gasket thickness for these engines, in the typical compression range we run. For a specific amount of thickness increase, the changes in CR will be a more on higher compression engines and a less on low compression engines

So it would take a lot to make a whole point change. But Cometic makes these heads gaskets up at least .125" thick so it can be done. Of course, you'll quickly ruin any sort of quench/squish gap you may have had when you thicken up the head gasket.