05 A .051 thick 1044 Fel-Pro head gasket was used to get the compression ratio of 10.3:1. This will give us plenty of throttle response because of the increased compression, but save the hassle of having to purchase expensive fuel additive needed by higher compression engines. Our test engine used -4.9cc pistons that were +0.10 out of the hole. Combine that with our 69cc AFR heads and the 0.051 head gasket we were right on target with squish and quench of 0.041. Make sure to use plenty of ARP white thread sealer on the head studs or bolts and Gordy recommends Gasgacinch on the both sides of the head gasket.