Anyone ever try to plug the compression release hole on a 400 cylinder.

 

smokin,

A few have, but by and large they don't gain any performance from it. The hole is just a blow by for sub idle speeds (like when you use the starter). Plugging it up would make very little difference at engine speeds above idle.

 

I have mine plugged, it raised the cranking compression 10 psi on a fresh top end. It's a compression leak regardless of engine rpm IMO.