6.To achieve maximum compression, Superior cut 0.065 inch off the head surface. The valve clearance was checked to make sure plenty of valve-pocket room was available for the 0.700 lift cam. After the cut, the head was measured with a 51cc combustion chamber for the final conclusion. So with a 4.030 bore, the deck of the piston protruding 0.003 out of the block surface, and 19 cc total dome volume, the 51cc combustion chamber produced a compression ratio a little more than 15 to 1. Of course, if you measure the compression ratio the engine builder's way, with the piston 1 inch in the cylinder bore, you find this calculation changes. In fact, if the math is done this way, the compression actually comes to 13.8:1.