In my feeble mind, a compression gage is all I need to compare the cylinder pressure readings
If they are not close to the same, it's time to start planning a rebuild.
Start with the heads, then cylinder wear and if you go that far, you might as well keep going on rings, crank bearings and cam.
Timing gears/chain also.
I have not rebuilt many engines, but every time I started with a valve job I end doing a full rebuild.
Don
