Adj vac advance on factory dist.

Strictly speaking the rate does not change unless the spring is changed, just the preload. Changing the preload changes the start and stop.

RustyRatRod said

Yeah, seems very few people paid attention to your cutaway photo. Makes it clear as a bell how it works. But people still argue.

Click to expand...

It's in the Chrysler Master Tech Conference. It's measurable with a vacuum pump. I posted this up 2018 and its easy enough to prove to ones self with distributor and a mity-vac or similar.