Okay I'm not sure the previous method was the best way so how do you carbed V8 guys have your advance plumbed ? Right now I have it T'd off of the intake manifold with one to the carb and one to the valve cover. Could someone show me a diagram ? BTW I am running an Edelbrock 650. Thanks guys.

Your vacum advance should go straight to the base of carb. Edlebrock AFBs have 2 openings at the base right below the idle mixture screws. Ones ported, others not. You want your advance to go to the one towards the rear of the car and just plug the one toward the back glass. I wouldnt have anything else t-ed into that one small line. Pull your other vacums from the big port at the carb base facing the distributor. The bigger hose to valve cover should come off the big port between the 2 smaller ports

[This message has been edited by rogergarrison (edited 04-03-2003).]

Do I still have to use a PCV valve ?

yes, you still need the PCV (Positive Crankcase Ventilation). This is just to let out blow-by, and the nasty gases that buildup in the crankcase. good place to run it to is the air filter box. it doesnt actually need vacuum, so it can be vented to open air.

Been there, done that.

Like Roger said, vacuum advance needs ported (sometimes called venturi) vacuum, not manifold vacuum.

Manifold vacuum (any vacuum drawn from beneath the throttle plate) is highest at idle. As the throttle blades open, the vacuum decreases. Ported vacuum is the exact opposite. As engine speed increases, ported vacuum increases, while manifold vacuum decreases.

The vacuum advance on a Chevy distributor uses ported vacuum to advance the timing. The timing needs to be advanced as engine speed increases, therefore you need a vacuum source that gets stronger as engine speed increases.

If you connect the vacuum advance to a manifold vacuum source, you will get full vacuum advance at idle, then the vacuum advance will actually retard the timing at the same time the mechanical advance is advancing it when engine speed increases. You will end up with unstable timing and virtually no advance.

Sorry for the long winded answer, but this subject seems to create a lot of confusion.

BTW- On Holley carbs, you use the port on the side of the front metering block.

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