I recently installed an HEI into my bird with the 350 and when I set the timing, am I supposed to plug off the vacuumn advance,or is it different with the HEI?I did plug it off and set the timing to 9DBTDC,but then checked the timing after I placed the vacuumn hose on the carb and now it says like 16DBTDC.Is this correct? Any help will be greatly appreciated.Thanks

Your vacuum advance should be attached to a ported vacuum source...no vacuum/advance at idle.

so I set the timing with the vacuumn line connected?

VACUEM LINE SHOULD BE DISCONNECTED WHEN TIMING IT

OK so once it is timed and then I hook up the vacuumn advance is it supposed to move to about 16DBTDC?

IT IS SUPPOSED TO ADVANCE WHEN THE LINE IS RECONNECTED,THE DEGREES IT WILL ADVANCE WILL DEPEND ON THE IDLE SPEED.

ALSO,THE MORE YOU REV IT UP,THE FARTHER IT SHOULD ADVANCE

Thanks for your help guys,you saved me some time.

ANY TIME.GLAD TO HELP

I don't believe the source is suppossed to have vacuum at idle.

THAT IS CORRECT 67 BIRD

Then if Redcoats set's the timing with the line disconnected..the timing should not change when re-connected..he needs a ported source...no vacuum at idle...vacuum anytime else...right?

that would be ideal but most of those parts have been removed over the years.you can run straight vacuem off the carb.unless you are lucky enough to have that vacuem port handy

The carb should have at least on ported connection...at least Rochesters do.

Hey Guys,


No wonder my 428 pings then because my vac advance is hooked up to the carb and draws a constant vacumn when the line is hooked up.I set it at 9 degrees and it pings so bad when it gets warmed up I retarded it to 4 degrees and it still pings some. I bought it this way so I guess I need to get the ported vac system for it to ever work right.This helps me with my 350HO Firebird too when I get it in and cranked.Does the timing stay the same no matter what cam you use??

Thanks Everyone,

Ray

Connect the vacuum advance to a vacuum line on carb that doesnt suck any air at idle. Theres 2 kinds of vacuum.

Ported vacuum - creates vacuum as rpm increases
Manifold vacuum - creates vacuum at low rpm

The vacuum advance needs ported vacuum to advance timing as the engines revs higher

or so i have read, and then set my system to run this way.