Power brake dual-vacuum question

[Jeff Erwin]

71 SBee 440x6. My power brake canister has 2 vacuum ports on a single connection. I've seen a ton of these, so I don't think it's unusual. One of the two was hooked to the PCV vacuum line on the center carb. Again, I think this was fine as I worked it out. However I am finally adding a PCV value so the engine is ventilated correctly (currently no PCV value) so that vacuum line from the center carb will go to the new valve on the valve cover.

My question is regarding the two vacuum ports on the brake canister. One is coming from the vacuum canister which is correct. What, if anything, do I now connect to the second port? Can I just plug it? Leave it open? Connect it to another vacuum source?

I have no idea what the inside of the brake canister looks like and I don't really want to take it apart.

 

[RemCharger]

The main vacuum hose should go from the manifold to the booster. What does this vacuum cannister you speak of , feed?

 

[Jeff Erwin]

The main vacuum hose should go from the manifold to the booster. What does this vacuum cannister you speak of , feed?

The vacuum canister is just there to provide vacuum to the brake system evenly regardless of engine rpm. The vacuum line from the manifold goes to the canister which then goes to the brake canister booster. Pretty standard, probably unnecessary but evens out the vacuum pressure.

What I don't understand is why there are two vacuum ports on a single valve on the booster. I see it a lot, but can't find any documentation that talks about it. Some boosters have a single vacuum port, some have the dual.

 

[RemCharger]

Some cars have extras that need vacuum.
68 69 charger headlights come to mind.

 

[R413]

They extra port on the power brake valve was to supply vacuum to the speed control. When a car didn’t have speed control that extra one would be plugged from the factory. There is no reason to have 2 supply sources to that valve.

The PCV hoses comes from the carburetor.

The vacuum supply for heater and headlights comes from the back of the intake manifold fitting.