vacuum advance

[shortbed]

Here's the story:
My '79 straight six (single barrel carb) has been hesitating a lot and until it is really warmed up it lurches and sometimes even warm it doesn't feel as though it's getting what it needs.
A friend of a friend, bless his heart, sucked on the vacuum line to the vaccum advance and said it wasn't operating properly and that was the problem.
But he also told me I'm going to need to reset the timing if I replace it.
I do all the work on my truck, but my manuals don't have anything to say about replacing the vacuum advance unit.
Could anyone walk me through this.

 

[elgemcdlf]

You will need to pull the cap & rotor plus tear down to the point you see the arm from the vac advance attached to the advance mechanism. There should be a small E-Clip holding that end on. Remove it & then remove the 2 screws holding the vac advance to the distributor. On a couple side notes most vac advances are adjustable using an allen wrench through the point the hose attaches. Secondly I seriously doubt the vac advance is your problem. Many folks don't even run it leaving it totally disconnected on performance engines. Sounds more like the accelerator pump in the carb to me.

 

[Fellro]

Some systems even used to block out the vac advance until the engine warmed up. Most hesitations in carbs like that do tend to be from accelerator pump inaction. Check to be sure the carb has a good squirt of gas when you work the pedal.

 

[Mil1ion]

How the heck did he pull the vacuum advance lever while attached to the springs?

You need to use a special tool to test advances not suck on it

 

[shortbed]

So you guys think its the accelerator pump and you think I should look down into the carb while I work the throttle and see if I get a good squirt of gas. Okay I'll do that and let you know what I see, but does anyone think it could be the vacuum advance?

 

[Fellro]

Here's the story:

A friend of a friend, bless his heart, sucked on the vacuum line to the vaccum advance and said it wasn't operating properly and that was the problem.
.

This is not the proper way to pull a vacuum anyway. You must hook some kind of vacuum pump, as the human lungs don't really have the pull needed to accurately check this. Besides, in order to see if it is working, you have to do this while the engine runs and watch the timing, or at least have the interior components visible.

 

[Mil1ion]

The Vacuum pumps can suck it with the engine not running and the cap off to see it move or not