[highway star]

Saw an article in hotrod mag stating most cars run better if connected to ported vacuum. I thought manifold vacuum was best. Could this be a misprint or do you think their right. Whichever hook-up produces better e.t.'s is what I am most interested in.

[tm454]

What kind of setup are you running? I have always used the carb hookup...had no problems...I have 3 pro-street cars and have always used the carb hookup for all of them.


Tazz


Rat Rods Rule!

[highway star]

Onthe front of the carb you have one vacuum hook-up that is above the throttle plates(ported vacuum) and another lower on the carb below the throttle plate(manifold vacuum). I have a 355 sbc ln a corvette that runs 13.9 at 100 mph. always looking for more speed.

[poncho62]

Depends on the curve in your distributer, and what you want for advance at idle. With manifold vacuum, you will have full vacuum advance when idling, leaving only the mechanical advance still to come in. Personally, I prefer to use ported vacuum for the advance.

[Silver_Camaro]

Get a spring kit to adjust your mechanical advance curve. Get it setup correctly then use the vacuum advance on manifold vacuum. At full throttle there won't be any vacuum advance, but mechanical advance will throw in all the needed advance if tuned properly. But on the highway at part throttle the vac advance will increase advance to increase gas mileage since the engine isn't under a heavy load such as WOT the extra timing advance won't cause detonation.

[Beenaway2long]

FWIW:
A knowledgeable builder told me ANY street car should be full manifold vacuum. Always.

[Rich1691]

That engine builder is right on the money!!!! Although some open plenum manifolds do not like it, for the most part, direct vacuum is far better for street machines. Many will run cooler as well.