Timing curve for my big-cam 451?

Bewy said
Dr C,
Not quite following where the 27* idle comes from because you say the VA doesn't pull in at idle? Does the extra timing come from the centri curve starting early?

Only the single superlight spring is holding the weights back initially. So, at a few hundred rpm, the weights advance until the loop on the heavy spring engages, which prevents further advance until about 1400 rpm which is above my idle speed. :) That loop happens to be 11 degrees, which is just right for easy starting and good idle timing!

I am surprised the VA does not pull in with 8" of vac. Admittedly have not worked with many adj Chrys VA units but those on GM HEIs will generally work with 5-6" of vac.

I don't know which Mopar distributor I started with... maybe it's some emissions thing that prevents early advancing. It did have a LOT of centrifugal advance. I'm sure the spring adjustment is all the way clockwise. I may experiment with another can, or just pay FBO the $69 (I thought they actually cut them open and install a lighter spring... but maybe not!)