Maniacmechanic1
solid fixture here in the forum
Most of the Trans Am Pontiac V8 Street guys use ported vacuum for advance Mike.Welcome AutoWiz. With a hot cam, I personally prefer ported vacuum advance for a more stable idle. With a hot cam, you (should) have a faster rate of mechanical advance - meaning lighter springs. Lighter springs have a harder time keeping the timing steady, especially with a lumpy cam and the carb usually being adjusted right at the edge of the idle/off idle transition. I find that ported vacuum advance gives a bigger "window" for a more steady idle.
If using an MSD ignition, it's nice that it retards the timing 20 degrees during cranking to help with easier starting of the engine (less kickback).
Does not work out with a True Race cam to spin 7000-8000 Drag.