I have not run the motor yet, due to some medical issues I had to take care of. It is 13.5 on compression, keeping the 2.20 valve. Didn't think there was good cost justification there with a 4.350" bore. I may have to use a very small amount of spray to hit my target for index racing and so the valve upgrade would be not too far from the nitrous cost I may need anyway. I'm sure ,dollar for dollar, spray is the better way! Bill