Is there anything it could be besides the rings, Already redid the heads. Would a cam cause low compression, truck has 310,000kms and not sure on the hours. and is it possible to change the one set of rings without pulling the engine?
I know yours is an OBS but my 6.4l is at Ford right now for low compression on one cylinder. Manual compression test showed 110 psi LESS than the other cylinders. They are stripping the motor down to the block now.