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MG MGA - Valve Stem Oil Seal

On dismantling my cylinder head I Noticed that the No.2 valve was missing its rubber oil seal. I have never noticed anything untoward and all looks good. Do they actually serve a useful purpose?

Steve
Steve Gyles

Steve, is this the stem seal or just the O ring below the collets?
Art Pearse

Steve,
those rubber oil seals (there are 8 of them, one on each valve) serve a very good purpose indeed. The prevent oil from seeping down the valve stem and going down the valve guides into the combustion chamber. If your valve guides are not worn much, not a lot of oil will seep down and the little that does will get burnt off in the chamber. They will surely serve their purpose if the valve clearances in their guides increase through wear. Before I R&R'ed my cylinder head I used to get so much oil in the chamber that the plugs were always soaking wet with engine oil, not to mention the white smoke from the exhaust.

Frank
f camilleri

Art

The little rubber O ring (Moss part No. AEK113).

I only have one spring per valve as it's a 1971 onwards 18V engine. Mine does not have the oil deflector (Moss part No. 1H725), although that part seems to fit on the 2nd spring that I do not have and is not shown on the 1800 head.

Steve
Steve Gyles

Hi Steve. The little rubber O rings are suppoed to stop oil leakage down the valve guide into the combustion chamber. In practice, those little rubber o rings in my experience are essentially useless! If your valve guides are worn at all, those O rings wont stop squat in the the way of oil! Proper oil seals can be installed if you are concerned about leakage and oil consumption. Better seals are usually available from aftermarket or British car suppliers Cheers, Glenn.
Glenn Hedrich

I'm with Glenn, they serve no useful purpose. They usually manage to break and vanish anyway.

Malcolm
Malcolm Asquith

I have no discernible wear in any of the guides. As I said in the opener, I could see not difference in the No.1 pot to the other 3. I have some spare O rings kicking around so I expect I will keep them in place.

Steve
Steve Gyles

I quite agree with Glenn about the improved aftermarket oil seals.They push fit on top of the guides and stay there. They do a much better job. However,when these seals are fitted the shrouds on top of the springs must be ommitted. If fitted they will ruin the seals the instant the engine is started.

Frank
f camilleri

Hi Steve. Bear in mind that it is easier to fit proper seals now with the head on the bench, than later, when it is mounted on the engine! Proper seals arent terribly expensive and would be useful if/when your valve guides start to wear. Just my 2 cents worth! Glenn
Glenn Hedrich

This thread was discussed on 20/11/2009

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