Vacuum advance

[peeeot]

I tried driving my car with the vacuum advance disconnected the other day and was expecting to notice a huge difference in pep and general driveability. Much to my surprise, I didn't really notice any difference at all!

My distributor is a replacement unit and when I rev the engine at idle in park with my finger at the end of the vacuum line, I do feel some suction, though it isn't very powerful.

Do I have a problem? :-D

[6TB1RD]

Do you have the 4100 carb?

The vacuum should not be all that strong. Another test you can do is hook up a vacuum line to the distributer with the car running and take a vacuum on the line with a hand vacuum pump with gage if you have one, and note the vacuum that the car starts to stall. you will see that it's not all that much.

if you do not have a vacuum pump then just give a quick suck on the line and see if she tries to die. if not you probably have a bad diaphragm. But check to see if you can move the advance by hand. take off the distributer cap and try moving the plate attached to the vacuum advance by hand it should move freely, if not the plate is stuck and needs cleaned and lubed.

you are not a lone with this issue I have had this issue with three cars I have owned.
Hopes this helps.

[peeeot]

I hooked up my hand vacuum pump and found out immediately that my vacuum advance isn't working at all! I've had this remanufactured distributor on the car for probably more than a year and with nothing to compare it to I didn't even know it wasn't working right.

It turns out the diaphragm in the unit was installed off-center and it didn't seal properly at one point. Now I have to locate a replacement somehow.

The local parts stores have one for $40, and that seems crazy to me for such a simple, common part. Can I use the vac. advance off a different year/make/model car?

[peeeot]

I bought a new vacuum advance at Autozone for $30. The salesperson on the phone must have misquoted the price. I've installed it, tuned the car and...

WOW!

I always thought the car felt sluggish for a supposed 300 hp, but it turns out the car was asleep with no extra timing advance under load. It's so much more fun to drive now, and so much smoother! It even shifts better!

Of course I suppose most of you know how these cars drive when they're working properly

[Guest]

Yes they do run. It's stopin that can be a problem. but one area you want to look real close at is were the arm of the vac adv. goes on the little brass stud. They wair a grove in there
and can and will cause a hesatation when you rest your right foot on the floor. (don't try for 140.129 is all your going)
...........Bill

[peeeot]

Thanks for the tip, Bill. The stud is in fine shape on my car.

The new vacuum advance claims to be adjustable. It says that if I stick an allen wrench into the vacuum port, the advance characteristics can be altered. I did a test with the car at idle around 730 rpm in park and a timing light . I added 8 " of vacuum and the motor was running really badly. The timing was out of the 10 degree marked range. Since it was at 6 to begin with, I would guess it had advanced around 10-12 degrees from that 8" of vacuum. Does that sound like it needs to be adjusted?

The car drives great and doesn't misfire or spark knock in normal driving. Only time I get any knocking is when accelerating briskly out of a 15-20 mph turn because the transmission doesn't downshift to 2nd

[bcomo]

George and Peeeot:

I checked my vacuum advance unit, and I can suck on the hose, and there is absolutely NO resistance at all -- like sucking air through a soda straw. Did I do that test correctly -- meaning bad vacuum advance?

I also checked the plate for movement with the vacuum arm still attached. It moves, but it takes a pretty had push with my screw driver to move the plate against the diaphram. Is that normal?

I have a pertronix (no points), but everything else should work the same. It still should need the vacuum advance -- right?

[Guest]

I don't remember what the specs are but i always gave those old fords 2 degrees more advance. They just seemed to run better. For the other ? go get a vac pump and take the cap off and see if it works. I have a mighty vac. You can check everything and bleed your brakes to by yourself. Hope that helps.

[bcomo]

I borrowed a mighty vac from Auto Zone and put it on the vacuum line to the advance -- ZERO vacuum on the diaphram. The arm doesn't move at all.

So, this means bad diaphram?

If I need to replace the Vacuum Advance unit, will the over the counter units do the same job as the OEM? Bird Nest has an exact replacement for $80 -- that's pretty pricey.

[Guest]

Yes! I don't know what auto zones looks like but it sounds like it works. Does your car hesatate or anything like that? If so that's your problem. Their is alot of moveable parts in that point plate that can be bad. Alot of people think carberator right away. That's not always the case. Bill

[bcomo]

It doesn't hesitate. I have it timed at 8 degrees.

I just wonder what difference it will make, if any.