Grab the rotor and see if you can move it from side to side (NOT rotation). There should be little or no movement. If it moves enough to see a visible change in the point gap, the bushings are shot. The breaker cam and the shaft that the rotor mounts on is mounted to the upper part of the advance assembly, and rides on its own bushing surrounding the lower shaft that connects to the drive gear. The lower shaft runs in bushings in the distributor body. All the above bushings virtually never get inspected and rarely if ever lubricated, and some of these distributors are 70-something years old.
Jerry
