Vacuum line

I Finally got a vacuum gauge so I can set up my carb. I think I got set up ok but I noticed a plugged line on it. Should this be hooked up or should I just leave it? Its a MC 2100 carb. the line is to the left of the fuel line with a black cap on it.

 

That nipple is ported vacuum that goes to the vacuum advance unit on a dual advance distributor, If your distributor have a vacuum advance unit on it thats where it gets hooked up to.

At idle there should not be any vacuum there, when you open the throttle you expose the port to manifold vacuum. Depending on what service manual you read it may be called venturi vacuum, ported vacuum or spark vacuum port. If you look inside its just above the edge of the throttle plate.

 

My distributor already has a vacuum line going to it...it seems to be running fine so I guess ill just leave it. thanks for the help.

 

The MC2100 carb you have has several ports like that. I'm assuming your dissy vacuum line is hooked up to the small port in the back of the carb. Then there is a big mother PCV port as well, obviously your PCV line goes there. If you have other needs for vacuum like a smokg canister or something you could use it, otherwise its fine plugged.
Short story: Its fine, leave it capped.

 

Brieoff is right, there could be more than one source of ported vacuum. Just for fun though you may want to put a vacuum gauge on the port your distributor vacuum unit is getting its vacuum from, There should not be any vacuum to the distributor at idle, If direct manifold vacuum is applied it will affect the initial timing if timed with vacuum applied. The correct port will allow vacuum to be applied to the advance unit as soon as the throttle plates are cracked just off of idle.

 

I'll give this a try tonight, thanks for the tip

 

I agree with Brian P about checking the vacuum at your dist.
:iagree: