[Stan Weiss]

Originally Posted by Jay S

With too hot of a spark plug the HEI will compensate at lower RPMs buy reducing the dwell at lower RPMs. It will run fine at lower RPMs with too hot of a plug. Once you get above 2500 RPM an overly hot spark plug will fame out and do what you are describing on the secondary air door.

If you happened to retard the cam timing the colder spark plug will help some, but wouldn’t correct it. The pumping compression reported does not describe a cam timing problem. Double checking the cam timing is probably the next step I would do after trying a little colder spark plug.

Jay,
This is my feeling also. But since he only did a cranking test on 4 cylinders that is why I think he needs to do all 8. There is always the chance that in manufacturing some lobes got mis-machined.

Stan