Quadrajet getting vacuum at ported vacuum

[Old60Driver]

G'mornin y'all!

Been a long minute since I've had any time to tinker, but finally got some. Ol' Blue is running great, but me being me, I wanted to check timing. Like I said, tinkering. I've been running my dizzy advance ported, and she seems to like it. With the vacuum disconnected, I have her set at 9°. But when I hooked up the ported vacuum, she jumps to 28°!! And that's at 850 RPM. Sure enough, I'm getting a good bit of vacuum from the ported post on the Qjet. I've never seen vacuum on the port at idle before.

Like I said, she runs just fine, and I'm guessing it's like I'm running it manifold, but I'm curious why I have that much vacuum on the ported point of the Qjet.

Any ideas?

 

[Ricko1966]

G'mornin y'all!

Been a long minute since I've had any time to tinker, but finally got some. Ol' Blue is running great, but me being me, I wanted to check timing. Like I said, tinkering. I've been running my dizzy advance ported, and she seems to like it. With the vacuum disconnected, I have her set at 9°. But when I hooked up the ported vacuum, she jumps to 28°!! And that's at 850 RPM. Sure enough, I'm getting a good bit of vacuum from the ported post on the Qjet. I've never seen vacuum on the port at idle before.

Like I said, she runs just fine, and I'm guessing it's like I'm running it manifold, but I'm curious why I have that much vacuum on the ported point of the Qjet.

Any ideas?

If it's jumping up like that you are not on ported vacuum,you are on manifold vacuum,or you are on ported and have the fast idle or throttle stop screw turned way too far in. Manifold Vacuum is actually the best choice in most instances. The diff between ported and manifold, ported no vacuum at idle,because the source is above the throttle plates which are closed,so no vacuum. Manifold vacuum is below the throttle plates so it sees vacuum even when the throttle is closed. Throttle open,Manifold vacuum and ported vacuum are the same. No vacuum advance at idle allows the mixture to burn latter so it burns more in the exhaust manifold ,for cleaner tailpipe readings at idle.

 

[Old60Driver]

That's what I was thinking as well. Engine totally warmed up, and not on fast idle. Actually reduced idle to 650 just to check, and I'm still getting vacuum that I can feel with my finger at idle. Definitely the on ported; drivers side, just above mixture screw.
FWIW, I was reading something by Cliff Ruggles indicating that some Qjets are made to not actually have a ported point. That essentially, they are all manifold. As I said, she starts and runs perfectly, so I'm not super worried about it. It's just....weird.
Investigation continues.