Hello,

Low compression and the 509 will cuase a very soft motor on the low end. Been there done that with the 6pak pistons in a .030 over 440 with 906 heads. Getting the comprssion up on that cam is a big help. When I changed cams I needed more p-v clearance. I taped the motor off and greased the heck out of each bore and piston top. Then I hand ground the necessary clearances. Bringing each piston to tdc one at a time to do the work. A good cleaning of course and put it all back together. Did this with the engine in the car. So if you are careful you can get the clearances it needs without pulling the motor.

Damon