I just finished a compression test on my 1946 Clipper.

The compression range was 70-85 PSI across all the cylinders except cylinder 4 was 45. When I put oil in the cylinders, compression went up to 85-90 across the cylinders but Cylinder 4 stayed at 45. My understanding is this points to a valve issue or head gasket.

Is there anything I can try with the valves specific to this cylinder before ripping everything apart for a rebuild?

I'm assuming you have a 282 engine; make sure you have some valve lifter clearance on both valves. In other words, just make sure lifter adjustment isn't keeping a valve from closing completely.

That an adjacent cylinder doesn't also have low compression suggests (but doesn't prove) that it's a valve problem and not a headgasket issue. You could pressurize the cylinder with compressed air and listen carefully to identify where the loss is coming from.

Thank You. That is the information I was looking for. I assisted with doing a valve job on this car with my Dad about 40 years ago. I am going to have to do a little research to remember the process, if the gap was set wrong back then, it was probably my fault.