Vacuum Advance - ported or manifold

[CHANMADD]

I have tried both ways over years, and without a doubt it is easier to get the motor to idle and respond to throttle without any starting or other issues with the ported , above the plates connection.With the manifold vacuum the initial timing has to be retarded too much. I also use a pcv which also taps into manifold vacuum, so a bouncing pcv can cause fluctuations........I think...Just runs great with the ported connection.

[Frank Messina]

Rupert,
Don't forget that you can also use an adjustable vacuum advance if you don't already have one that enables you to tailor the amount of vacuum advance exactly to your engine's needs. All you need is a 3/32 allen wrench which I think you have. In this way you can avoid light throttle detonation by backing out vacuum advance while still maintaning a fairly quick mechanical curve all in by 3000 RPMs. For example I have mine dialed back to 7° vacuum plus 15° initial which allows for easy cranking but a very crisp throttle. Total advance at 3000 RPMs is 35° with no vacuum present. HTH
Frank
PS: Oh and yes, use manifold vacuum only, not/never ported for all the reasons listed above.

[SuperHart]

You know, Frank, you may have given me an idea. At idle I seem to be running awfully rich. I run a pair of Holley #8007 carbs on a Price Motorsports dual quad intake. I wonder if it is because I have the idle screws nearly closed all the way to get the idle down to 800 RPM since I have so much vacuum advance at idle (24 degrees) plus initial advance of 10 degrees. I'm going to dial back the adjustable vacuum advance to 12-14 degrees and then open the idle screws on the carbs to bring the idle speed back up. Let's see if that helps some.

[mreid]

You should be plugging vacuum advance when seting idle speed and base timing.

[Jeff Frigo]

get a new distributor without vacuum advance problem solved it's just not necessary in that light of a car