Andy, what rpm have you gone up to? Also, is the power curve still rising at the end of the pull. In theory, if the heads/cam combo can support the higher rpm, one would assume there maybe more power available but I don't know if that would higher rpms would suit this motor with the 4.15 stroke. I would think 8500(or a lil higher) maybe the highest plateau but who knows, I'm not a skilled engine builder like you guys, just a young student.