SMSP header thermal 3" exhaust test pipe. My guess was the compression was in excess of 11.0:1. Head was fitted with oversized flat faced valves, plus being decked thin gasket etc. Was a very strong motor. This was also on 95 octane Sunoco so the timming got really agressive when tuning. For all motor H22 is def the way to go. Poor mans K swap. imo