Hooking distributor advance to intake manifold port.

[carpart67]

I'm trying to give my car a budget tune up and enjoy a few drives with whats left of summer. I've been reading/researching and have determined that hooking my vacuum advance to a manifold source is probably the best way to go for my application. Oddly enough what should be the manifold vacuum port on my Carter AFB has no vacuum at idle. I plan to rebuild the carb this winter and will hopefully figure that out then. For the time being is there any reason I can't connect my vacuum advance to a port on my intake manifold? (there's a capped spare there already) Thanks!

 

[downsr]

It would be okay to do that

 

[KitCarlson]

It is possible that manifold vacuum will advance timing, reduce engine braking at coast down, lopy coast feeling, and result in high idle speed, under light engine loads. Loads such as A/C or alternator draw from running loads will bring down speed, but you may notice instability, if you desire to adjust and maintain correct idle speed.

When working on the carb, manifold port comes from the base, ported source is from slit passage above the throttle plate.

 

[downsr]

Yes it will advance timing and make it idle higher.Just turn the idle back to where you want it

 

[RustyRatRod]

That's how the Carters and Edlebrocks are. They do not have vacuum at idle on either port. As soon as the throttle is cracked, one has ported vacuum and the other manifold. The port that's down low on the driver's side is manifold vacuum.

I agree though that for a street car it will probably pull too much timing in ad part throttle, unless you back off the initial timing some and that could take away from the bottom end. On a street car, IMO ported vacuum is best all the way around on vacuum advance. Just my 2 cents and probably worth less.

 

[RustyRatRod]

Yes it will advance timing and make it idle higher.Just turn the idle back to where you want it

Not with the AFB style carbs. They do not pull vacuum at idle from either port, as I explained above.

 

[67Dart273]

I don't care for manifold vacuum on modern street cars. You need to recurve the dist to suit. FBO seems to be 'big' on it.

 

[TrailBeast]

Just to add a little clarity, if you connect the vac can direct to the intake vacuum source (NOT on the carb, but intake itself) it WILL pull your advance higher at idle and cause adjustments to be necessary to compensate for advanced idle timing bringing your total timing down too low.
If you connect it to a port on the carb that only has vacuum as you open the throttle, then fine.

For economy at mid speed cruise you want ported vacuum. ( meaning vacuum comes in with throttle opening.)

 

[TrailBeast]

That's how the Carters and Edlebrocks are. They do not have vacuum at idle on either port.

My 1406 does.
It has one ported and one manifold, and the manifold is the only one with vacuum available at idle.
Ported is on the left and above the throttle plates, and manifold is on the right below the plates and has idle vacuum.

I just recently went through the whole thing to replace my adjustable vac can and adjust it so I am positive about it.