It's probably the 1/4" one with the rubber cap. Run a length of vacuum
hose from it to the vac advance on the distributor and see if your fuel
mileage doesn't improve significantly.
It is possible that the car runs well without the vac advance. MG
didn't use vac advance for years--at least through TFs. The car can run
well w/o it, but will run even better with it.
On Fri, 22 Jul 2005 19:32:03 -0400 Mike Torrusio <firstname.lastname@example.org>
> I found three openings on my intake manifold:
> one a nipple about 1/4 inch which is welded shut;
> one a large pipe about 1/2 inch or so, which I suspect would
> go to the emission canister by the right fender (which is non
> operative), and that is also pounded closed and welded shut;
> another nipple of approximately 1/4 inch which has a rubber cap
> over it.
> Nothing else.
> Could it be that my distributor hasn't had anything attached all
> time and would it still run as well as it has?
> Michael Torrusio, Jr. 1971 MGB