Ok, I just got a 700 CFM Holley Classic Double Pumper, and I noticed that the vacuum port at the back of the carb is for the PCV, and that there is no prevision for a power brake booster. So I tried hooking the brake booster up to the intake... but that provided WAY too much vacuum and had nearly no brakes (hard as a rock and wouldn't stop). So for right now I hvae my brake lines hooked up to the PCV port on the carb, which provides awesome vacuum, the brakes work great, but if u stomp on it they lock up and u stall. So what I want to know is since there is no provision for a brake booster, where is it SUPPOSED to be hooked up, and will it cause any harm leaving it hooked up to the PCV?? Need to know soon cuz that's how i'm still running it. Thanks.

 

You won't have any problems hooking it up to that port... but you should hook up the pcv to it and run the booster to the manifold... which is what i did and my breaks work great... i don't understand how its pulling 'too much vaccuum'... maybe you can get a vaccuum regulator?

 

Nah, I tried hookin up the brake booster to the intake directly, and my brakes got stiff as a board. I could push the pedal a max of about 2 inches, and would take 100 ft to stop from 30 MPH, and that's definately not good. So the main thing I wanna know is, is there anywhere else I should hook them up, and will it cause any damage having the brake line hooked up to the pcv and not using the pcv at all anymore?

 

It sounds like its not pulling any vaccuum at all... I used the port right behind the carb.. it was like a 3/8 npt fitting. You can keep that brake line hooked up to the port on the carb (just keep a check valve on the line to the booster... which it should already have); now for pcv... you could run it into the manifold or some other vaccuum source. I dont know how your not getting any vaccuum thats weird...

 

There's no such thing as "too much vacuum", so don't worry about that.

The port on the back of the carb is what we've all used for all these decades, just like a Q-Jet, with a "T" for the PCV. Some intakes have a port behind the carb that also works, if you put in a suitable fitting; but others either don't have that, or it's so close to the carb flange that a Holley sec bowl covers it up.