These are simple pictures of my P-90 head that I'm using on my turbo car. All I had done to it was a valve job and the top and bottom of the head decked just enough to make sure they are straight. The cam is stock but, should be fine for my application. Some day I'll spend the big bucks and have fully built head done by one of the big shops that do L series engines. This one has the mechanical lifters vs. the hydraulic lifters of the P-90a. Both heads have the same combustion chambers but, the P-90a has self adjusting lifters controlled by oil pressure. The advantage of the P-90 is that you can run higher RPM's without any issues from the hydraulic lifters. Nissan had been putting exgaust liners in thier heads for emisions reasons but, left them out when they did thier turbo heads for extra exhaust flow. On some boards there has been a big debate over which head is better the P series or the N-42 for best flow. I went with this because it was what I had and is a proven design.
