According to the KB catalog, the piston has comp height of 2.057, the step head is 0.075". The total of the dome and the valve reliefs ADDS 4.8cc to the head volume. This is a common mistake, KB is the only company that talks about reducing chamber volume with a dome as NEGATIVE ccs. So adding to the volume above the piston comes in at POSITIVE ccs.

According to the KB website, their stated compression ratios are for zero deck, 0.040" head gasket, 0.030 overbore.

For the KB236 and 88cc heads the stated compression ratio of 9.9:1.

If you do a Web search for the KB236 you will most likely go to the Summit catalog page and they have their own compression ratio computer, which uses the positive ccs for the piston dome and dish as subtracting from the combustion chamber volume. If you use the KB numbers in the Summit calculator you are guaranteed to get wrong answers. Guaranteed.

Using a deck height of 10.725 and stock piston and rod lengths puts the piston 0.025" down in the hole, which with your 0.020" gasket puts your setup the same as the KB standard, give or take a few cc. But if your heads have not been milled, they are 88 to as much as 93cc, meaning your actual compression ratio should come out between 9.75:1 and 9.9:1.

It might run on pump premium, or need a little water injection. IMHO it's on the upper limit.

One other thing, the thinner head gasket and the 0.075" step are helping fight detonation, I wouldn't change that.

Other things that will help are keeping the engine and intake manifold cool, and keeping the mixture on the rich side.

R.