I think that I get it. When the piston gets to the top of the stroke with a chamfer the "squish" goes 2 ways, part of the charge goes the right way toward the combustion chamber to create turbulance and part goes the wrong way towards the chamfer. This (if I understand it corectly) would have the same effect as not as much quench with a straight edged piston. Like .040 with a chamfer is maybe the same as .060 without one even if the 2 compression ratios were the same. Am I on the right track? Jay 6155