Rochester 2GV what is the port for?

[jackk]

I've got a 1969 LeMans with a 2 barrel Rochester Carb. There is a pipe coming out of the bowl. This would be near the bottom to the left if you are standing in front of the car. It goes to a 3 port valve near the front of the engine.

What is this for? I've looked and looked, and every expanded view of this Carb doesn't show this. I can only guess it is either used for the vacuum advance or it is some vent that is used to help the carb deal with atmospheric pressure or hot temps.

Furthermore, my 3 port switch has this hose, a hose that goes to the rear of the carb, and a missing hose. My vacuum advance is also missing a hose. This is a new car for me, and I'm not sure the best solution.

 

[dheupel]

Here's a couple photos of my carb setup on my '69 LeMans 2bbl. Hopefully these will be helpful

 

[jackk]

More Pictures

Thanks for the pictures. Here is the way mine came. I just noticed today that the one hole is not plugged. I hadn't seen it before! I'd still like to know what that tube to the carb is for, I'd like to abandon the vacuum temp switch if possible. Just have the vacuum advance go to one place.

Since we are sharing pictures, any idea where the ground should go on my idiot temp light sensor? That bare wire there makes the light go on, so I just need to complete the loop.

For those looking, it can be easier to right click on the picture link and open in a new tab.

 

[melsg5]

the tube going to the carburetor is the vacuum source. Once the valve hits a certain temperature it opens directlng the vacuum to what looks like the vacuum advance on the distributor. It's hard to tell where the second line is going that is running along the top edge of the valve cover. You have a broken wire sticking out of the wire harness that should connect to that blue terminal. You have the wrong switch, should be single, but it should work if correctly wired. The ground for that circuit is the body of the switch screwed into the intake manifold.