Bottom of single plane intake manifold has small "vacuum line attachment?

[JohnMc]

I have a '70 124 with a 1438 with single plane intake manifold. On the underside of the manifold in the center there is what appears to be a small vacuum metal tube assembly that is screwed in that the PO has blocked off with a hose with nut in it.
I am going to be replacing the original carb with a Weber 32/36 DFEV and wonder if what I am calling vacuum metal tube assembly is supposed to go somewhere (and if so where), be plugged (by putting a bolt in the bottom of manifold) or be open to atmosphere?
Thank you all very much.

[baltobernie]

If the opening is very small, perhaps 1-2 mm, that port was originally designed to suck fumes from the vapor canister. If you don't have one of those, then keep the opening plugged. You won't be able to tune the carburetor otherwise.

[JohnMc]

Much appreciated!