The Stovebolt Site Forums The Shop Area Engine Shop 305V6 Idle problem-update

Okay, I have read and re-read the replies to my 305V6 idle problems, and I have discovered a new problem. The distributor cap on my truck has a sliding window that would allow me to adjust the points without having to take the cap off. I had the window taped open so I could watch the breaker plate as it advanced the the ignition. I found something disturbing. With the vaccum advance hooked up, and the truck at idle, the vaccum advance is all the way open, instead of being at rest at idle. When I unhooked it at idle, the engine ran smooth. When I hooked the vaccum back up, it advanced the timing. I took the distributor apart, and besides this problem, a grounding wire had broken loose and I fixed that. I put the distributor back together after finding NOTHING, started it up, and the advance was fine. It was at rest at idle with the vaccum hooked up. I revved it up a bit, and it advanced like it should. But, after a few minutes, it started acting up again. It wasnt advancing it all the way, just a little bit.

What the crud is going on with this stupid thing? I have it at idle, but its drawing too much vaccum?! I have it hooked up at the back of the carb and not the intake manifold. what should I do? is it a bad vacumm advance mechanism? :mad: :mad: :mad:

Hook up your vacuum gauge to the advance line with the advance disconnected and see what kind of readings you get. Should go up considerably when yourev the engine. My guess is a bad advance. You could also put a tee in the line with the advance connected, but I doubt if you have one laying around.

It would appear that you are getting full manifold vacuum applied to your vacuum advance, which is not a good thing.
I would, first of all, make sure that you have the vacuum advance hooked to the correct port.
After that, it is possible that there are leaks in the carb that are allowing full manifold vacuum to reach the vacuum advance port. There are two possible causes: 1. The carburetor was rebuilt with the wrong gaskets the last time it was apart, or 2. there is sufficient wear on the various parts (throttle shaft, etc) to allow full manifold vacuum to the vacuum advance port.

A vacumm advance should never be hooked to the manifold vacuum, by the way. You can also check the advance canister by using a vacuum tool to check whether it is leaking.

I do in fact, have an extra Vaccum tee. I hooked it up inline with the vaccum advance. At first I tried it just hooked the carb and left the advance out of the loop. It showed 5 inches of vaccum. I revved it up, and it went up to about 15, and when I let it idle down, it slowly went down to 1! I hooked the vaccum advance up to the carb and had the gauge inline, and it showed the same. It would not go to 5 again, it just stayed at 1. WHen I revved it up, it once again went to 15, and when I let it idle, it went back to 1.

in response to Vaughn, it is hooked up to the carbs vaccum advance port. The throttle shaft is worn pretty good. I checked the new gaskets I used for the re-build, and they were Identicle in every way.

Only way to fix it is to bush the throttle shaft. If you don't have the equipment to do it yourself, you can either find a carb rebuilder or buy a rebuild, if one is available.