I had that issue. I added a 1/2" locking collar to the distributor shaft and it eliminated it entirely. I did use a dab of loctite on the threads, installed the collar loosely, bolted down the distributor to position the collar and the removed the distributor to tighten the locking screw tight. Reinstalled it and set timing.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)