I just installed new points and condenser in my 69. I'm attempting to set the dwell and timing and I noticed when I removed and plugged the vac advance hose no difference. The engine still idles a little rough. I hook the hose back up, reach in with my hex key to adjust points and the the advance starts working and the engine idles up some and smoother. I pull off the hose again and idle goes down and rough again. Again I hook the hose up and nothing happens until I touch it with my hex key. Should'nt the vac advance work some just by plugging back up to the distributor or is it sticking?

------------------
jodysss396 (or Jody)
1969 Chevelle SS396
Fathom Green
Numbers Matching
TC member #921
A.C.E.S. #4348
Jody's 69 SS396 (http://chevelles.com/showroom/69jodysss3962.jpg)

You're right, the engine should speed up as long as there is vacuum present in the hose when you connect to the advance. Check for vacuum at the hose with engine at idle. Got vacuum? Next take the cap off and see if you can turn the rotor (clockwise I think) and it should spring back. If it doesn't return you need to clean up the moving parts. If that seems good then it could also be just a stubborn vacuum advance. Go get 'em!

------------------
Never be afraid to try something new.
An amatuer built the Ark,
Professionals built the Titanic.
Team Chevelle Gold #33
ACES Member #02913

Thanks Tom. All parts are working freely. I have plenty of vacuum to the advance. I've taken off the vac advance and it my just be stubborn or weak for sure. Is that something I can get at a parts store like Autozone?

------------------
jodysss396 (or Jody)
1969 Chevelle SS396
Fathom Green
Numbers Matching
TC member #921
A.C.E.S. #4348
Jody's 69 SS396 (http://chevelles.com/showroom/69jodysss3962.jpg)

<BLOCKQUOTE>quote:</font><HR>Originally posted by jodysss396:
Is that something I can get at a parts store like Autozone?

[/B]<HR></BLOCKQUOTE>

Jody, you should get yourself a Crane adjustable vacuum advance. I got one for my HEI and if my memory serves me it was right around $20. It`s an easy install and you get the added flexibility of tuning your spark curve.

Finally something that doesn't suck! http://www.chevelles.com/forum/smile.gif You can buy a replacement part that all you need to do is install it.

------------------
Never be afraid to try something new.
An amatuer built the Ark,
Professionals built the Titanic.
Team Chevelle Gold #33
ACES Member #02913

I think your breaker plate is sticking. That is what moves when the vacuum advance works. If it's a stock 69 there should be no vacuum advance at idle.

Jody, understand you are working with two different advances in your distributor. When tom talks about turning the rotor clockwise and having it turn back, he is talking about the mechanical (centrifugal) advance which is controlled by engine speed. When setting timing neither advance should be working. Thus the term "inital timing". Set with the vacuum disconnected and the engine RPM low enough to prevent the mechanical from kicking in.

To check the mechanical advance, set the inital and then slowly raise the RPM's watching the timing mark, it should porportionately climb higher to full mecanical advance at about 2200. This varies from car to car.

You can check your vacuum advance by this crude method, Again return your car to idle and pull the hose off of the carb and slowly suck, yes I said suck, on the hose Keep it quiet guys, you can operate the vacuum advance this way, again watch the timing light, you will see the timing and hear the difference in RPM. What usually goes bad with the vacuum advance is that they get a hole in the diaphram and require too much vacuum to operate them. If you need to keep on sucking on the diaphram, then it is ruptured and needs replacing (very common).

Of course, there are tools to be able to do this, but you can get by with what I said. Vacuum advances are engine specific if you need to buy one. Hope this helps.

Thanks, Bill

It also depends on whether the advance chamber is connected to ported or manifold vacuum. The vacuum advance in most of these cars is connected to manifold, which means it will have vacuum all the time. That's not a hard, fast rule however. Sometimes, the engine just runs better when the distributor is connected to ported vacuum. With ported vacuum, you only have vacuum at the hose when the throttle plates are cracked open.

Thanks to all. Went to Autozone and bought new vacuum advance for $6.99. All working perfectly now. The car wants to smoke tire when kicking down from high gear now. New points and a correctly operating vac advance made a BIG difference. I kinda hated to take the old advance off because I feel it had been on the car since new. Thanks again everyone.
Jody

------------------
jodysss396 (or Jody)
1969 Chevelle SS396
Fathom Green
Numbers Matching
TC member #921
A.C.E.S. #4348
Jody's 69 SS396 (http://chevelles.com/showroom/69jodysss3962.jpg)