I know of a Ford racer that thought he had 14 to 1 comp. ratio and the motor made peak power at 7100, he took it to a good machine shop that check all of the measurements and found that he had a actual 11.4 to 1 ratio. They order new pistons and made sure that they ended up with 14.7 to 1 and the peak hp (with no other changes, jetting, timing, LSA, valve springs, type of fuel or nothing else) moved up to 8400 rpm and gain a bunch of power. I can call him and get the exact differences and so on if you want. That Hemi is real hard to get to much compression in just like Hemifred said, I guarentee it. The tighter you squeeze good gas before you light the fire the better it will burn and the more power it will produce.