As some know I run the N-42 head. After researcing for a week now, I have found that the head is not too good for turbocharging applications. The chambers have a recessed squish are by 2mm or .080". If you look at the chamber on the P-79 or P-90 you will notice the squish are is just about even with the bottom of the head. This forces air/gas into the combustion chamber on the up stroke of the piston. It makes for a better combustion and creates good swirl for a more homogeneous mix and burn. I have sent my head to be shaved .060" which will give me about 9.2:1 for my new turbo motor. For $400, rebello racing would weld up the squish are, blend the chambers(heart shaped) and mill the head back flat. Unfortunately, I have to build the motor by this weekend. Anyway, the hot ticket for a detonation free head is to use the E-88 and have the chambers welded in the squish area. You will have small chambers, but if you use the dished piston L-28 you should be able to retain a decent streetable compression. Rebello says they have a street motor surviving at 11:1 with no pinging. FYI.