Bronze distributor shaft gear wear

I’m not sure exactly how a collar helps- because the torque to turn the oil pump isn’t going to rapidly change. The cam gear provides the driving torque which pushes the dist gear down onto the bushing. There would have to be some kind of vibration rapidly loading and unloading the gear for it to move up. Since the whole engine is a vibration creator I suppose that might be causing the movement.

Lots of folks report a collar stabilizing timing so I have to agree a collar does help.

What I’d like to be sure of is why this bronze gear failed so rapidly. It was obviously pushing down hard onto the bushing which wore away enough to let the gear ride low on the cam gear. I’ve made a bunch of measurements and compared to my spare 340 and cannot find anything.

One of life’s mysteries I guess….