Correct about the rpm window, but that motor ran out of smoke right at 6,000. Still had another 500 rpm which is plenty to make more torque, and power. If the torque curve carried a little higher so would the hp. I'm going to go with the cam mostly on that one. The heads can flow what ever, but if you can't get the valves to open/shut at the right time it's not going to work as good as it should.