i ran a n42 , but relocated the head temp sensor since the n42 didn't have one. ran it to the coolant thermo housing. also used a 2mm hg to lower compression to 7.8:1,,, with a 1mm hg, it's like 8.5:1... my n42 had a hair line crack between the #6 valve seats, but i didn't care and put it on anyways.. lasted for a while, then got worser and coolant was leaking into the combustion chamber. then went back to the p90 head