Couple of things you might try. First, I would take a real close look at the vacuum advance/octane selector plate and make sure the copper tang is not completely worn away. Next, I would take the distributor cap off and put a chalk mark reference on the body where the rotor is pointing. Then loosen the screw on the vacuum advance, not the bolt, the screw. Wiggle the distributor and push down. The distributor may not be fully seated. Tighten the screw and make sure the rotor is still pointed at the chalk mark. If the distributor moved downward, you should probably consider resetting the timing. Next, I agree with the others. Pull the grease cap and remove the stem. Dig out the spring and then fish around for the little Bakelite disc that rides on the distributor shaft. If it’s missing, or completely worn away, that might be part of the problem. Clean out what you can. You will have to install something. Deve found a nylon washer that fits. Check his website for the number. I had some delrin discs cut from some delrin rod. Install a disc or washer, repack with some clean grease, clean out the stem and cap real well and repack both with clean grease.
