What kind of vacuum(ported, manifold) does each vacuum accessory require?

[crazypete]

Right now I've got cruise control, egr and the smog dump valve. I've got everything hooked up to ported vacuum right now (the brake port providing vacuum for my vacuum guage, brakes and cruise) and the spark port feeding vacuum to the egr, distributor and dump valve. Is this going to work this way?

I'm trying to make a "true" street legal carb conversion

[PKRWUD]

Okay, first we're going to work on your definitions. There are two kinds of vacuum that you will deal with: Ported vacuum and Manifold vacuum.

Ported vacuum comes from a single, small tube on the carburetor. If it's a Holley, it's the tube coming out of the passenger side of the primary metering block. This tube supplies the vacuum for the vacuum advance on the distributor, and that's it. If you don't have a vacuum advance, then plug this port. The way to verify if you've got ported vacuum is to check it while the engine is running. Manifold vacuum is strong at idle, and deminishes as you open the throttle. Ported vacuum is the opposite; almost none at idle, but as you open the throttle, it increases.

Manifold vacuum comes from the intake manifold, usually via a tree mounted on the rear of the intake. The ports on the throttle plate of the carb are usually manifold vacuum as well. The source for your power brakes can be taken from the intake manifold, and the PCV vacuum source will be the large port on the throttle plate, usually facing the rear. Any other items that require vacuum are tapped into the vacuum tree on the back of the intake. If you are using an EGR, you will need thermal vacuum switches to control the vacuum going to it. Otherwise, it will always be open, and you won't be able to start the engine, or control it's idle.

Get it?

Take care,
~Chris