indy500

66 Cutlass, 330, OEM setup

First, going to borrow a vacuum gauge in the next day or two, but in the meantime, I set the timing to about 8 deg at idle with the vacuum advance disconnected and the hose plugged. I thought I would get a jump in the advance after plugging the vacuum advance in, but really didn't seem to move. Since I don't have a gauge at the moment, I did what I think would be a 'poor man's test', suck on the vacuum hose going to the distributor and observe the advance change. If I really pull as hard as I can, I can get about 4 or 5 degrees of advance. Does that indicate my vacuum advance unit is faulty? I have no idea what a normal human sucking on a hose is going to pull as far as inHg, but I figured it would be enough to get more than a couple degrees of advance. By seeing a few degrees change, I'm guessing it's hooked up correctly.

Any thoughts? Pull the vacuum advance unit off - is there a way to test it?

BillK

Can you feel vacuum on the hose that goes to the advance unit ?? Some cars do not have vacuum until you open the throttle some.

oldcutlass

If you plugged into a ported vacuum port you will not see an increase at idle. If you move the hose to a manifold vacuum port it should send it to max advance.

indy500

Yes, at idle I can feel vacuum on the hose when I put my thumb over it, and it pulls the golf tee upwards and into the hose when the engine is at idle. So, there's some vacuum there at idle, but no change in advance

oldcutlass

If there is vacuum you probably have a bad vacuum advance can. Mine was bad when I first got my car. You can buy a Crane curve kit for a points distributor, comes with springs, a stop, and an adjustable vacuum advance. If you don't want to recurve the distributor right now, just put those parts away. Or you can just go to the parts store and get a stock non adjustable unit.
https://www.summitracing.com/parts/crn-99601-1

indy500

Hmm. I actually found a new one in my parts box, so apparently I ordered on last fall and didn't remember. I can tell you first, that my 'poor man's test' isn't going to work, or at least just with a hose connected to the can and me sucking on it, I can't really move that shaft hardly at all.

So, with my hose connected to the carb, and the other end to the vacuum advance unit that I'm holding in my hand, I also don't see the shaft move when I plug/unplug it from the hose. Maybe I just have fairly low vacuum at idle and need to adjust that? Will check that on Monday after I get the gauge. If I rev the engine, I see the rod pull in on my stand-alone unit. So, I'm getting enough vacuum at higher rpm's to pull that what seems like the full travel. Think the next step is really to adjust idle screws based on the vacuum gauge.

oldcutlass

Are you connected to manifold or ported vacuum? You may get a little vacuum at ported, which is why they say to disconnect and plug the hose when setting timing.

indy500

I'm plugged into the front of the carb, so I'm assuming that is ported. And manifold would be if I was plugged into a port down on the manifold itself?

joe_padavano

Easy test. Temporarily connect the vacuum advance hose to a direct manifold vacuum port, not one on the carb. If the timing moves, the advance can is fine. If not, it's bad. Keep in mind that the problem COULD be a leaking canister, or it COULD be a stuck point plate. I would refrain from buying any parts until you figure out which is the cause.

indy500

8 degrees advance at idle, without vacuum advance.
33 degrees advance when connecting the vacuum advance to manifold vacuum.

joe_padavano

So your vac advance is working fine.

indy500

Thanks everyone. I think what was messing me up was the ported/manifold difference.

oldcutlass

Glad you got it figured out.