Olds Scott

Where can I hook up a temporary guage on my 324 for adjusting my Rochester 4GC mixture screws? My ears aren't what they used to be.

oldcutlass

Any available full manifold vacuum port.

Olds Scott

Thanks oldcutlass but which one? Distributor vacuum advance port, vacuum wiper port.

oldcutlass

I'm not 100% familiar with your year engine. Is the wiper port from the manifold or vacuum pump? Is there an available port on the manifold itself? Is the vacuum advance manifold vacuum.

Olds Scott

Not sure if it is a constant vacuum source.

Ozzie

The vacuum advance is ported; so that's not so good.

The wiper vacuum motor feeds through the pump's booster; so that's not so good.

On the 4GC there is a full vacuum tap at the rear of the throttle body which connects to the pump's vacuum booster. On mine there is a "T" fitting; one side goes to the vacuum booster on the fuel pump; the other end has a plug which could be used for a vacuum gauge.

The only problem I'm having is remembering if that "T" fitting was always there from the start or if I added it somewhere over the life of the car to get some pure manifold vacuum to do exactly what you are proposing. Anyway look at the back of the throttle body part of the 4GC. Right in the center of the back there is a "tap" (1/4" NPT???) If there is no "T" fitting (the factory may have used an elbow), you could add a "T" which would make your task easier in the future.

Olds64

You can also set idle mixture screws with a tachometer. Set them for maximum idle speed.

Olds Scott

Thank you Ozzie and Olds64. Running a PVC valve in line with out road draft tube and with power brake vacuum hose. Would have to find a fitting to run a third vacuum outlet. Will try the tach idea first.

DFitz

The tach works fine. I used a tach on my '55 2-barrel. I would however not adjust to max idle. Initial adjust to max idle, then back off about 1/4 turn. You don't really want the idle mixture that lean. It will hesitate and stumble.

As an alternative, if you can smell gas in the exhaust, it might be just about right!