What should be the cylinder pressure? How much variance should there be? I think I may have a blown gasket.
From my research, normal compression is 50 to 75 psi. I suggest doing a leak test. Do this for each cylinder. Roll the piston to top dead center and put low pressure air in through the spark plug hole. Might have to make up a fitting. Plug thread is 1/2 inch NPT. To much air will cause the engine to move if all is good. Listen for hissing at the carb….intake valve leaking. Hiss at the tail pipe…burnt exhaust valve. You could also feel around the head for air escaping and listen at the next plug hole for a hiss. Also listen at the oil fill…that would indicate piston ring bypass. And also possible bubbling in the rad. Hope this helps.
Thank you. That is a thorough analysis. I did make up a fitting. I tested cylinder 3. Definitely hissing through 4. I should followup with some of you other suggestions. I did check to see if there was antifreeze in the oil . There was none.
Most welcome. If your getting a hiss between cylinders, I would be suspect of the gasket, as long as othe things check out. I would also suggest that if you end up pulling the head to replace the gasket, use a copper gasket and a copper head gasket spray. It will help with the sealing of the gasket as long as there is no serious crators in the block or head. Good luck!