Just so you know. Normally, crankcase pressure can push oil up the distributor shaft. If you have good control over the pressure, and it seems you do, you may have worn bushings or the lower theist washer is worn/missing.
The distributor is in a live oil port.
Remove the distributor and inspect it for sloppy bushings, worn thrust and even a worn gear can tear up the bushings causing then to huff.
It can be frustrating.
Good luck. The parts to repair it are available, but might be easier and cheaper to pick up new/good used one.
Good hunting.
GT
