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MG MGB Technical - Proper head breathing

Firstly, I greatly appreciate the learned advice I receive here.

This is something I always wondered if I did correctly. While I have a 1971 B with a GB block I put a 1967 head and carbs on it.

In doing do I put in a PCV valve and a non vented valve cover. The smog stuff is long gone and the valve cover does not connect to the carbon filter any longer.

I do use a 'vented' valve cover cap. Moss PN 460-102 and I have an alloy valve cover Moss PN 224-508

The cap fits loosely on the valve cover not like it did on a OEM non vented cover. I figured the vacuum would suck it down into place. I'm not crazy about the alloy valve cover but its on. In comparison I think the OEM is better. Just eye candy really.

Is this a proper set up for what I've mentioned?
Max71

Max you can get a chrome vented cap that fits the alloy cover. If its working right you should get a change in revs by removing the cap at idle. I like the fit of the OE cover as well but as you say alloy looks good. I get the gasket to fit well by using contact or similar on the cover only then fit loosely over night till stuck then tighten up. Only ever tighten as you would with a screwdriver when using cork. Denis
Denis4

"The cap fits loosely on the valve cover not like it did on a OEM non vented cover."

Bad valve cover then. If the chrome filler cap fits better and is ventilated then that's fine. However someone here has recently done that after problems with the correct plastic filler, and he said that whilst the cap is ventilated it isn't filtered like the original which isn't so good. There is also a question over the size of the vent - if it is too big you can get excessive oil consumption via the breather system, but if the revs do change when you remove the cap it should be OK.
Paul Hunt

Do you think I should get a large O-ring to have it seal better. I believe the revs do change once removed but it is loose and I've tried several new ones.

I read up on the cap and saw several posts about how the plastic one is very good. I can order the chrome one which appears to have filter material in it.
Max71

When I installed an alloy valve cover on my '67 B, several years ago, it came with a vented chrome oil filler cap. It doesn't leak oil and allows the engine to "breathe" properly. RAY
rjm RAY

Max71 - are you referring to the plastic cap? That should have a rectangular-section seal that forms a taper to seal to the inside of the filler hole rather than flat on top. You could try adding a thinner O-ring between that and the upper part of the cap, to push that down a bit, and hence be pressed tighter into the filler hole when the tabs are engaged.
Paul Hunt

I'll try for a o-ring and order the cap that I guess should have come with it if that fails.
Max71

This thread was discussed between 18/10/2015 and 20/10/2015

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