11. I used a set of aluminum Trick Flow heads (part number TFS-30400006) that helped increase the horsepower numbers and reduce the total engine weight. I ordered the Trick Flow heads from Summit Racing along with most of the other engine parts. The heads are 195cc intake runners with 62cc combustion chambers. Since we looked up the piston dish, around (-12cc) and the depth of the piston in the bore when at TDC (-0.032), I was then able to calculate what the compression ratio was roughly going to be by entering the numbers in a compression calculator I found online. I calculated the compression right at 9.6:1 with a 62cc head and a 0.015 Fel-Pro head gasket.