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MG MGA - Breathing

I've just been donated an aluminum rocker cover, only problem is it doesn't have a breather pipe just a vented cap.

I still have the breather pipe on the tappet cover which is vented downwards to atmosphere, but what are the consequences of using the non vented aluminum cover?

At the moment its on the car which is fitted with an 1800cc engine and appears OK.
John Bray

Hi John. It should be easy enough to drill and tap a hole in the alloy cover and to fit a threaded stub for your crankcase vent hose. Cheers, Glenn
Glenn Hedrich

If it has a vented cap that should suffice (not just a small hole). Air must be able to enter the rocker cover in some way or the side tappet cover tube will not be able to extract the waste gases, pariculaly the water vapour formed.
One thing with a vented cap, it should have some type of air filtration system. You do not want dust to be drawn in there.
A better solution would be as Glenn says and drill and tap a hole in the cover and fit a tube to the air cleaner, as in the standard arrangement.

M F Anderson

I have had the common alloy valve cover with no real vent. The cap with a small, ~1/16" hole will cause oil to collect in the cover ribs. I'm not sure of the path the oil takes. But I was constantly cleaning up the oil. I drilled and tapped a brass hose fitting for the original vent tube. the oil seems to stay in the engine now.

I did switch to K&N air fliters at the same time. I can't imagine that would have been the difference.
Chuck Schaefer

I went to the local AutoZone and found an Edelbrock filtered breather that fit the aluminum valve cover perfectly. Works like a charm, I've run it for 5 years that way.

Chuck Mosher

This thread was discussed between 28/04/2010 and 30/04/2010

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