Vacuum Issues/Routing

So after a comment over in my ARA A/C Rebuild thread. I hooked up the vacuum line to the dizzy and, well, it's now causing PROBLEMS, not solving them.

My dizzy did not have any vacuum line hooked to it and the idle/drive was smooth as silk. After hooking it up, my idle has a bounce to it now. Feels like it's missing a cylinder/hesitation every 3-5 seconds. I'm going to pull the line back off (and reseal the end) and see if it goes back to the smooth idle.

So, I've been searching through old threads and photos and diagrams and can't figure out what's happened or why that seems to have messed up things.

So I've got the standard two way valve and a 5 way valve off for vacuum lines.
On the 5 way - I've got:
1. Brake booster
2. Tranny
3. Cruise control (that doesn't work)
4. Dizzy
5. Rear Carb diaphram
The 2 way:
1. Other dizzy pickup
2. Capped line

So anyone got any thoughts? Remove the cruise line and swap it to the other dizzy pickup so that I can completely cap off the two? Am I missing another hookup to the carb? I've got an open port from the rear near the air cleaner, but it's far larger than any tubing I've got.

I'm going to throw some pictures in here and hopefully that'll help illustrate some of my words.

The larger port at the back carb is a fresh air return port for the choke preheat on the manifold.

So you have a dual port distrib, one side was manifold vacuum and the other was ported vacuum. So one side would retard the timing and the other would advance the timing.
1st thing I would do is with a vacuum pump check both ports on the distributor to see if they hold vacuum.
If they both hold vacuum, then you need to see if the vacuum sources are going to the right places.

Do you have a vacuum diagram chart for your year and applicable smog set up? Calif or Federal?, High altitude or sea level?

Been so long since I messed with any of this stuff, I need a chart to be sure or else I would be guessing...

Hi, there is a clip holding the throttle linkage which is bent in 1/2 so check that out.
It looks like the elbow on yop of the PCV valve needs a cap.
I don't see the Ported vacuum switch in the thermostat housing.
The nipple on the bottom of the air horn went to the air cleaner. You should cap it off if you don't use it.
A breif description from my Chilton's manual. If you are keeping it original you need a better vacuum hose diagram.
Good luck

904Bronco said:

The larger port at the back carb is a fresh air return port for the choke preheat on the manifold.

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Gotcha. I'll check the manifolds, but doesn't hold vacuum, so it's OK to be left open?

904Bronco said:

So you have a dual port distrib, one side was manifold vacuum and the other was ported vacuum. So one side would retard the timing and the other would advance the timing.
1st thing I would do is with a vacuum pump check both ports on the distributor to see if they hold vacuum.

Click to expand...

Gotcha. We'll see what comes of this.

904Bronco said:

If they both hold vacuum, then you need to see if the vacuum sources are going to the right places.

Click to expand...

Probably gonna do this before the test.

904Bronco said:

Do you have a vacuum diagram chart for your year and applicable smog set up? Calif or Federal?, High altitude or sea level?

Click to expand...

Kind of. I've got a few from chiltons, haynes, and the inter-webs. But as always, things have been changed so I'm trying to make sure that I've got it right. Federal. Sea Level.

B RON CO said:

It looks like the elbow on yop of the PCV valve needs a cap.

Click to expand...

Thought that too. Will cap with some capped hose in case I need to use the nipple later.

B RON CO said:

I don't see the Ported vacuum switch in the thermostat housing.

Click to expand...

Noted. Will investigate.

B RON CO said:

The nipple on the bottom of the air horn went to the air cleaner. You should cap it off if you don't use it.

Click to expand...

Will do.

B RON CO said:

A breif description from my Chilton's manual. If you are keeping it original you need a better vacuum hose diagram.
Good luck

Click to expand...

But does the fact that I would have no advance/retard to the timing make sense for a smooth idle and when I hooked it back up, it got rough? Should I then lean towards a leak in the top vacuum connection?

There is mechanical advance in the distributor in addition to the vacuum, so you may have been getting by with that.

If you hooked up a vacuum line to the distrib and the internal diaphragm has failed, now you have added a vacuum leak which leans out the mixture and could affect your idle.

904Bronco said:

There is mechanical advance in the distributor in addition to the vacuum, so you may have been getting by with that.

If you hooked up a vacuum line to the distrib and the internal diaphragm has failed, now you have added a vacuum leak which leans out the mixture and could affect your idle.

Click to expand...

UGH.
Thanks for the advice!
Love solving a "problem" and creating 5 more downstream!

Hi, distributors with the dual vacuum / retard cannisters use the inner port for the retard function. If you eliminate the retard function, plug the vacuum hose but leave the cannister port open so the diaphragm can breath. The black hose with the red stripe looks like it is going to the retard port on the vacuum advance cannister.
If you don't have a $40 Mityvac hand pump you may think about getting one. You can put a vacuum hose on the outer port and suck on it. If the distributor cap is removed you should see the breaker plate move. If you block the hose with your tongue the breaker plate should stay out. If it just sucks air the diagram is shot, and as mentioned, you have a vacuum leak, and you notice it as a rough idle. Good luck

On your distributor remove the cap and twist the rotor by hand and let go. That is your centrifugal advance. There are springs and weights that are under that move and spring back on their own. if it doesnt spring back by its self it needs some work under there. The vacuum canister on your truck has 2 ports the back port has a retard timing function and the front end port is a vacuum advance function. Take a piece of hose and put it on each fitting and suck on the end of the hose. if it acts like its plugged that is good. If it just sucks air that is bad and the canister needs to be replaced.

The vacuum lines on the distributor vacuum canister if hooked up properly on the end port canister with the engine at idle there should be no suction in that hose. If you rev up the engine it should start to pull suction. Suction at idle is bad and probably hooked to wrong port at the carb. No suction at idle and no suction when revved up is bad and the port is probably plugged at the carb and needs to be cleaned.

The back port on the canister is a problematic one especially on your engine. That vacuum line is supposed to have manifold vacuum on the line when the engine is warmed up. Your engine originally had a vacuum port switch heated by engine coolant so vacuum would not have vacuum on that line until the engine reached certain temperature I do not see any of that engine control stuff. there were other heated switches and all of that worked with Egr and other parts of your smog system.

At a minimum you need to test the vacuum advance diaphragm to make sure it's good. Then you need to run a hose from the front port of the diaphragm to the ported vacuum port on the carb. It's on the passenger side middle just in front of the choke. You can just leave the rear port on the diaphragm unhooked for now.