Try this:
Remove the distributor cap.
Grasp the rotor and turn it until it stops, then release it. It should return to a solid stop without assistance. What you will be feeling is the counter weight springs functioning. If the rotor does not return to a hard stop, you will need to take the distributor apart and inspect the counterweights and springs for excessive wear.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission