86transamws6

there are 2 vacuum ports on the front, which one is for the timing?

mrr23

should be the one on the passenger side. the one that's higher up from hte base of the carb. it has no vacuum at idle.

AJ_92RS

Uh...... you DO want vacuum at idle for a vacuum advance dist.

Why else would it be called vacuum advance?

I don't recall which one it is, but if you have a vacuum gauge it's easy to find. Hook it up and if there's vacuum at idle, but none when you quickly open the carb to wide open throttle, then that's the one you want.

It's been so long since I've messed with one I don't remember which one it is exactly.

MikeS

I don't recall which is which offhand. With the car at idle, just uncap them one at a time. One will have vacuum, the other will not. Once you know which one does not, you've got it.

Odyssey

It's the one on the passenger side. You don't HAVE TO HAVE vaccum hooked up to the distributor by the way. But if it's there, use it!

mrr23

uh NO you don't want vacuum at idle there skippy. learn something here today. at idle you do not want the vacuum. as the rpm's increase, the vacuum will rise. then it will advance as the vacuum rises. if you put it on the full time vacuum, it will fully advance at idle. the vacuum port is above the throttle blades, which is why there is no vacuum at idle. when the throttle blades open, it will suck through that port and create the vacuum at that point and pull the advance pot. you want timing to increase as rpms rise.

you do it your way and you reverse the mechanism operation. at idle it will add all the timing. then when you open the throttle blades it will retard the timing.

86transamws6

thanks guys

MikeS

Did you get it hooked up? How's it running?

AJ_92RS

OK... here's a pic I found at (can you guess?) www.edelbrock.com

As you'll see, the port on the passenger side is for Timed Vacuum Port for emission controlled vehicles.

The one on the driver's side is for Manifold Vacuum Port for non-emission controlled engines.

Here are some instructions that they give.

That should clear it up for ya.

I guess it really revolves around what type of distributor you have. I've always had ones that used a full vacuum source, so there was vacuum at idle, but slowly diminished as the RPM increased.

mrr23 has obviously used more timed vacuum advance systems.

So I guess we both were right..... but now you have to find out what system YOU have.

86transamws6

well i hokked it up to the passenger side, it has vacuum at higher rpm's, the other one always has vacuum, my distributor is vacuum advance. with it hooked up to the passenger side now, i just dont feel the power, i think ill try the drivers side then?

MikeS

I believe the only difference between the two ports occurs at idle. Off idle, ported vacuum is the same as manifold vacuum. I don't see why it would give you a lack of power. All that hooking it up to the other port will do is give you more advance at idle. Is this a new carb installation, or did you just have to remove it for something and are putting it back on?

AJ_92RS

Yea.. Mike's right. There shouldn't be any difference when you push the go pedal. Seems as though you've got other problems besides the vacuum advance.

The only difference with the two is vacuum at idle. I've always used the driver's side because every car I've ever had a carb on had a radical cam and it just idled better.

mrr23

yes there are both types of distributors. emmisions years started as early as 1973. but my 79 z28 needed the part time vacuum. what you may want to do is find a vacuum diagram for the engine the distributor came from. you will find very few of the full time advance distributors.

Apeiron

There's no real difference in the distributors apart from the advance curves, which is the first thing everyone changes anyway.

mrr23

ok i'll clarify for you. there are 2 types of vacuum advance pots. one where it advances as vacuum increases. and the other that advances as vacuum decreases. that is what needs to be found out. and even then some pots have a 10* advance and some have a 16* advance. usually the mechanical advance part has 10* capability. but again most will be the one that advances as vacuum increases.

CamaroGurl07

I know that this post is very old. But i have a problem with the car dying when put into gear its a camaro and was computerized.. i had to put a lock up kit on the transmission was wondering what side what went to. i'd like to have my car run properly. any help would be apprecitated.

patricks85z28

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1929ModelA

1985 K5 Blazer, stock 350 with MSD vacuum advance distributor (HEI) part number 8362. 1906 edelbrock ASV2 Carb. Just got off the phone with edelbrock tech. Tech says that you want to use port on the passenger side (emissions side). If you check with a vacuum gauge, you will see no vacuum at idle (pass side). Driver side (non-emissions side) you will see vacuum at an idle. Tech at edelbrock I spoke to said that the instructions are poorly worded and everyone in the tech department is trying to get edelbrock to change the way it’s worded. Having said all that, I called MSD and they say you Do want vacuum at an idle???? Then I found this article from superchevy. Read this article!!! I get it now!

http://www.superchevy.com/how-to/add...nition-timing/

hope this helps someone one day!

Fast355

iTrader: (2)

Hope this helps you even though the tech on the phone sounds dumb or atleast ignorant. Ported or Timed vacuum is a BS emissions era crutch. You want the vacuum advance connected to manifold or full time vacuum. It will help the engine run cooler and give you a smoother idle. Will also allow it to idle with the throttle plates more closed, preventing the carb from idling on the transition slots.