Motorcraft 2100 Help

Hey guys,
I have been tuning on my 2100 for a while now and I think I have found the problem.... I think.

On the valve cover side of the carb, there is a copper tube pertruding out of the lower portion of the carb. It is obviously a vaccume due to when the Jeep is started it sucks right at idle. Now that I found it and capped it the Jeep seems to run better(duh). Well, when I go to start it and lets say it doesn't fire, it would spit that vac plug off the carb. So, I swapped in a smaller plug, but should it do that???? Also, once I plugged that port it pulled the idle down considerably, is right correct.
If it helps, I have no smog junk on it and I am running a HEI ignition so I only need one ported vac, correct??
Thanks in advance,

High5:stout:

 

sounds like it was/is supposed to have a hose hooked up to it, PCV etc??? (manifold vac)
If you not using it, plugging it off would be okay.
A vac leak would cause a higher engine idle speed, so capping it would bring it back down to normal.
If the Jeep were to "backfire" then yes it could blow the cap off. Either a snugger fitting plug/cap or maybe a clamp added should do the trick.
ported vac would be used for dist vac advance and/or emissions controls.

 

Yeah, I have a ported vac for the dist. I didn't realize that was a vac. of any kind. I realized it while tinkering this afternoon. I was polishing my rims and adjusting the timing. I did cap it off and after it blew it off I put a tighter cap on it. It should hold.

Thanks for the help,

High5:stout: