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MG MGB Technical - Weber PCV Hook Up

I'm driving a 1970 MGB with a Weber DGV set up. It runs well,with good accelleration and generally good manners. When I installed the new carb, I ran the hose from the Smiths style PCV valve to the tube on the tappet cover. I noticed that there is a hole (5/8" or so) on the underside of the air cleaner adapter plate which I have seen hooked up to the PCV valve. Should I be concerned, or at the least plug this hole to prevent unfiltered air from entering the carb?

Thanks,


Peter Van Syckle
Peter Van Syckle

Peter. Plug the hole. It is used with the RB conversions because you have to, at the very least, use one hole on the intake for the brake servo unit. Your system should work fine and, by blocking the hole, you will be cutting down on the possiblity of getting dust and dirt into the intake system.

Les
Les Bengtson

As usual, sound advice from the Great State of Arizona.
Thanks, Les.

Peter
Peter Van Syckle

correct me if im wrong, but isnt the hole he is talking about is for the crank case vent to go into, and on the manifold it should be a tapped hole for the brake servo
James

I have a DGV and have a hose from the breather tube on the tappet chest cover connected to a hole in the air filter housing. This allows the oil vapor from the tappet chest cover to be burned up, emmissions control stuff. My intake manifold has a fitting for the brake servo and since it is not used it is plugged.
Henry

James. That is correct. On a Rubber Bumper car, one having a brake servo, the single tapped hole in the various Weber intake manifolds, is used to power the brake servo.

However, on cars that do not have a brake servo unit, the hole may be used to plumb in a PCV valve as Peter has indicated that he has done.

In such case, the hole in the carb filter, should not be open to the atmosphere. All of my filter units have been supplied with a filter having such a hole as a piece that can be punched out, if necessary. In such cases, the air flow thought the very minor openings is not of significant value. If one is concerned about them, a thin bead of J-B Weld 5 Minute epoxy is sufficient to seal them.

In the case in question, the hole has been, already, opened up. Also, due to the fact that there is already an adequate crankcase ventilation system in existance, the existing whole in the carb air filter serves no useful purpose. (As it does on my daugher's 77 and my two 79 Bs.) Thus, in such instances, and in such instances only, it should be plugged to prevent unfiltered air from entering into the engine.

Your system is, also, perfectly correct. You decided to run the line from the front tappet cover to the air cleaner (as with my three cars) and, I suspect, it works quite well.

Otherwise, you would have had to do as Peter has an install a "mushroom" type valve into the spot on the intake designed to house the vacuum input for the brake booster.

Both of you are doing "the right thing", but in different ways. To the best of my knowleldge, neither method is "superior" to the other method. Both work and seem to meet the required desires--less emissions.

I would suggest that Rob Edwards be our model. The environment is to us, our children, and to our grandchildren, a very important thing. We should, to the maximum extent possible, try and keep out cars well maintained and in the best possible tune.

In my experience, that will make them as "green" as possible. Something I am, very much, in favor of.

Les
Les Bengtson

This thread was discussed between 17/05/2006 and 18/05/2006

MG MGB Technical index

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