I'm installing an edelbrock intake and carb on my 71 chevelle. Which vacum inlet(on the carb) is for the vacum advance on the distributor? driver or pass side?or are they both the same thing? thanks guys

The port that is highest is ported vacuum. There will be no vacuum at idle and will make vacuum as the throttle blades open...the lower port is manifold vacuum..there is vacuum prestent at idle and will decrease as the blades open...I always put it on manifold vacuum....but its best to try both and see how your engine responds

so after deciding which is best to use, then you'd just block the other one off?

Originally posted by pegleg71:
so after deciding which is best to use, then you'd just block the other one off? yup

Yes just plug the other one. I would bet that 95% of the time the full vaccum is better. I wouldnt even mess with the ported, I have tried that and it always just causes trouble. Some people think that when your cruising down the road your not making any vaccum on "full" but your prolly pulling 15" or more so it is present at cruise.

Ok cool. that would explain a few things. thanks guys :D

thanks for the help guys. I ended up using the manifold vacum and its run good so far-
- frank

Out of curiosity, why run manifold vacuum to the dist. advance ? why would you want to advance the timing at idle ? Are you getting a stronger signal thruout the off idle RPM range from it?

Originally posted by BLK64SS:
Out of curiosity, why run manifold vacuum to the dist. advance ? why would you want to advance the timing at idle ? Are you getting a stronger signal thruout the off idle RPM range from it? Car will idle alot smoother with the vaccum advance hooked up to manifold usually and you may also notice the engine running cooler at idle cause the exhaust tempatures are cooler with the extra advance.

Car will idle alot smoother with the vaccum advance hooked up to manifold usually and you may also notice the engine running cooler at idle cause the exhaust tempatures are cooler with the extra advance.

With that being the case, why not set the initial timing higher, and limit the total ?

Originally posted by BLK64SS:
Out of curiosity, why run manifold vacuum to the dist. advance ? why would you want to advance the timing at idle ? Are you getting a stronger signal thruout the off idle RPM range from it? Thats exactly why I had to do mine, because to get my car to idle I had to open up the butterflies so much I was losing the idle circut. When I would accelerate I had a lean condition up to 1500 rpm's. I plugged it in to direct vacuum which brought the idle rpm's way up and I could close the butterflies up. Now Im running 28 deg' of intial and seems to like it. It had 12 deg' of intial on balancer before and the vacuum canister added 16 crankshaft deg'. Im using a edelbrock carb also.