Help with 340 compression + cam change

Honestly, I wouldn’t worry and I would focus on the cam change at hand. Changing the cam should be done carefully because we now know the compression is at a spot where a reasonably size performance camshaft can kill this engines low end.

So think before you leap. ;)

If it were I, I would not increase the intakes duration but only at a max of 6*’s. But it is also the cams timing events. A catalog cam “may” not do what you want it to do. At least installed straight up or as recommended. I’d look for an early intake valve closing to help build cylinder pressure.

If you take a catalog cam and adjust where it is speced to be and move it for an earlier intake closing, you’ll also change the rpm band downwards a few rpm. It will still make more power.

You might want to call a grinder for a custom cam and simply tell them your engine is at 8.5-1 ratio.