Vacuum Advance - Manifold or Ported

[Frank Messina]

Originally Posted by John S Peterson

Isn't another benefit of manifold vacuum to dist is more initial timing when running but easy cranking?

Yes and sort of. Initial advance is what you set with your timing light with the vacuum lines plugged and is present all the time and is your starting point for everything else that gets added in (vacuum and mechanical). Vacuum advance is an add in that shows up once the engine is running at idle ( manifold source) , is present at cruise and normal acceleration and disappears at WOT. And you're right, it is easy cranking. Ported vacuum advance was Detroit's effort to reduce Nox at idle by reducing engine timing and was the beginning of a long decline in engine performance. End of history lesson.
Frank