tworottiedogs

With the predator, there are no vacuum ports for the distributor. I bought a T-fitting and was going to splice into the manifold vacuum port for the brake booster. Will that work? Another option could be to drill a port on the carb spacer. Will that work?

Any better options?? :confused:

The Dude

I'd go with adding a fitting to the spacer and use manifold vacuum for your brakes. I don't think you want your brake booster sharing vacuum with anything.

Also you want your distributor connected to a "ported" vacuum source. A quick-and-dirty way to tell the difference between "ported" and "manifold" vacuum is that ported vacuum comes from ABOVE the throttle blades while manifold vacuum comes from below them.

[EDIT: Well, somebody got in and explained "ported" vs. "manifold" while I was editing. Now you have it from two sources... :seeya ]


[Modified by The Dude, 4:03 PM 1/18/2002]

Larry B.

There are two types of vacuum, Ported and manifold. Manifold vacuum is used for most things like accessories. Some distributors also use manifold. This comes directly from the intake manifold. Ported vacuum is vacuum created above the throttle plate of the carb. Some distributors used this along with some emission stuff. Manifold vacuum is highest at idle and no load cruise. When you open the throttle the vacuum drops and then slowly builds as engine speed increases. Ported vacuum is zero at idle and increases with air velocity thruogh the carb. Now you know. :)

tworottiedogs

So, both the brake booster hookup and a port in the carb spacer would both be manifold vacuum and not work for the distributor? That is very, very bad!!

Is my only option to go with a mechanical distributor?

Vetterodder

All vacuum is taken from the intake manifold but ported vacuum is "switched" and is only available when the throttles are opened. If the carb doesn't have a ported vacuum source, ported vacuum is not an option. You should still be able to run vacuum advance (unported) with the T you bought but just not ported advance.

Larry B.

I have found over the years, when you modify anything, everything else will work just a little different. One set up may work very well with manifold vacuum to the distributor while another similar set up my work better with no vacuum advance at all. Always try as many options as you can. sometimes it will surprize you. The only thing for sure is each set up /car combination will be different. Even stock stuff that worked great in the past may not do so well on today's gas. :D


[Modified by silvervetteman, 5:53 AM 1/19/2002]

MassVette

I asked the same question, and it was suggested that I use manifold vacuum. Works real good............
:yesnod: :chevy :chevy :yesnod: