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MG MGB Technical - Valve Stem seals - O ring type

Hello,

I'm just a bit confused about the O ring type valve stem seal. When I removed the head, only the inlet valves had the more modern 'cup' type seal fitted (the same as on a ford pinto engine if that helps anyone) - which must have worked well as no smoke at all was visible.
However, in my new gasket set I've got the old O ring type seal, and I just don't see how they work. Surely once the valve is depressed won't the o ring ride up the valve stem and just sit there ? If so, how does it seal ?

Thanks in advance

Colin M......
C E Muir

The oring fits above the valve retainer and under the lock and is compressed between the two. The orings work by making the oil coming down from the rocker flow out to the edge of the retainer (i.e. outside the diameter of the spring) before it flows downward. It doesn't seal the valvestem so much as just direct the oil away from it.

HTH!
Rob Edwards

Just to clarify the terminology, I've never quite figured where the O-rings should sit wrt the collets. Do they go between them and the valve cap?
Steve Postins

Thanks for that Rob, I've never seen valve stem seals of this type before and never imagined putting them there !!

Colin M......
C E Muir

When fitted as Rob said they work as well as any
and outlast all others. Denis
DENIS4

Steve

There is a recess in the valve cap to retain the seal. Fit the spring and cap, compress the spring, fit the o ring seal, fit collets, release spring compressor and that is that (in theory).

Peter
peter burgess

Aha - now I know what I did wrong! Many thanks
Steve Postins

This thread was discussed between 30/04/2008 and 02/05/2008

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