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MG MGB Technical - Weber/PCV connection question

Hello all,
I just bought a '77 B with a weber carb. I've never had a B with this before. The PCV hose off the side vent is just hanging down. Not good.

I can't see any place to hook into manifold vacuum unless I tee off the brake servo fitting.

Any ideas?
Thanks! David
David Steverson

Check the archives. There are discussion on this especially for MG's with carbon canisters.

Brit-tek often recommends going to a road draft tube like the early MGB's. That's probably what you see.

I've got the same questions regarding my 65 that has the diaphragm PCV valve that feeds into the intake manifold.
Robert McCoy

David. Which Weber carb? If it is a DGV series, you need to get the air filter which takes a 90 degree elbow fitting and hook that up to the front tappet cover. If it is a DCOE, that may not be possible to do.

Avoid the "road draft tube" if at all possible. There was a reason that MG did away with it.

Les
Les Bengtson

Webers don't have a PCV port unlike the 69 and later SUs as they don't have a constant low-level vacuum area in the carb that SUs do. With a Weber you really need to retro-fit a pre-69 PCV valve to the inlet manifold and connect that to the port on the front tappet chest cover in order to have adequate crankcase ventilation. Just connecting that port to an air cleaner is the very early (pre-PCV) system that the road-draught tube was part of. It is very hit and miss, ventilation-wise, and also disables the anti-run and charcoal cannister purging systems.
Paul Hunt

Don't tee off the hose between the power brake check valve and the bake booster as this will bleed all the vacuum for the brakes as soon as the engine quits running. Not only that, but the rear 2 cylinders will run leaner than the front two, even with a PCV valve.

The front and rear branches of the intake manifold need to be "teed" together and the branch connected to an inline PCV valve that connects to the side cover. A PCV valve from a 70s-something big three 4 cylinder will work - it's only a controlled vacuum leak.

Depending on the intake manifold, there may be bosses on the branches already that can be drilled out and tapped. If not, it's easy to add them.

Wayne
Wayne Pearson

Thanks for all the comments!

Les, I have no idea on the model, this is the first Weber I've owned. I'm already thinking of going to SU's, only because I know how to work on them.

Dave
David Steverson

"I'm already thinking of going to SU's"

Good plan! Webers add nothing except problems and complexity unless part of an overall power improvement programme.
Paul Hunt

Dave, the DGV is a downdraft carb, the air cleaner will sit on top. The DCOE is a side draft carb with dual throats. The DGV's when properly setup work fine. The DCOE is much more of a headache to get properly setup and unless you are runninng a highly modified engine don't do much more for you then eat more fuel. The SU's are more then adaquit for a stock or mildly modified motor, and a lot less of a headache.
John H

Well, that's it! SU's it is. Now, to find some...
David Steverson

David,
Maybe I can help with finding some. You have email.

John
John Bradshaw

John, I just found this and sent a reply.
Dave
David Steverson

This thread was discussed between 03/06/2008 and 05/06/2008

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.