jfox55

Question about the vacuum ports on my edelbrock 750. My question is, there are 3 ports on the front of an edelbrock carb. I know the location of the middle but am concerned the person that built my car may have hooked the 2 small outside ones up back wards. The one on the left has no vacuum at idle and when you open it the vacuum increases. The other side has tons of vacuum at idle and none when you open the car up. It sounds pretty common scense to me, that the one with no vacuum at idle and alot when you open it up should be hooked to your distributer vacuum right, so it can advance timing as you mash it. Right now mine is hooked up so I get alot of vacuum at idle then when you mash it it gets no vacuum which I think would actually decrease your advance at wot, right. Am I just thinking of this wrong, or is the way it should be. Please reply quick.

RB83L69

You're right, but for the wrong reasons...

What vacuum advance does is increase the advance when vacuum is high (low load) but RPM is high (throttle open). This occurs when cruising. This extra advance is for gas mileage. It goes away under high load. You don't want it at idle either, so it's derived from a port just above where the throttles sit at idle, which only exposes it to vacuum when the throttles are opened off idle.

Move it to the port with no vacuum at idle, and check your tune for optimum timing (which does not invole a light) i.e. adjust the timing to where the car runs the best.

jfox55

since I am switchin the distributer vacuum to the port with no vacuum at idle I will have to adjust my air/fuel mixture since it was adjusted off of the other side which had alot of vacuum at idle right.

Jer82Z28

you might have to readjust your idle mix. but reset your timing and idle speed first. The guy who hooked up your carb, might have retarded the timing to get it to run right.
otherwise I would think you would be experiancing detonation

jfox55

What should the timing be set at. My engine is in my sig.

ronterry

I would play with 36 to 38 total @ 3000rpms, and as much initial as you can without it looping to bad.

That might be hard with a stock HEI. Setting the total is where it's at. To many people worry to much about initial? not even knowing there total. Can you imagine setting it to 2 degrees but the total is 32 or something. Power wasted. or dumping 10 degrees initial, and detonating all to hell on the top end, cause the total is over 40.

With a good MSD or Accel distributor you can use stop bushing, and lock that timing right where you what it. It's easier than having the distributor curved by a performance shop.

Ron