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Valve stem oil seals?


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I've got the head off my 1972 GT6 to inspect and clean up but before I removed the valves for cleaning I though I would check to make sure all parts are available for the rebuild.
Then when I checked the workshop manual and parts catalogue there was no mention of valve stem oil seals, do these engines not use them, and if not how is the oil prevented from draining down the stem into the combustion chamber?

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These engines do not have them as standard and nor do the 4 cylinder ones.

First point is that when your rocker gear is in good shape and correctly fed as Triumph intended (no un-metered external feed pipe), there isn't a great deal of oil up there anyway - just enough to lube the important bits.

Second point is that when the valve stems and guides are in decent shape, there isn't much gap for the oil to escape through.  In fact in my experience, even when the guides are quite worn, not much oil is lost that way.  The difference in oil consumption when I went from very slack guides to new ones with stem seals on my Vitesse was negligible.

If you have an external rocker feed and worn guides (helped by worn rockers and shaft) then it will be a different story.

It is possible to fit seals.  Ford Pinto ones will go on the standard guides (just) but only if you are using single valve springs.  Chris Witor sells bronze guides with the inlet ones machined to take stem seals and the matching seals, which can be used with double valve springs.  The guides are not cheap but are top quality.  Chris doesn't consider exhaust valve seals are necessary - the inlet guide potentially sucks oil down, but the exhaust valves blow it back up.

Bottom line, if the head components are as Triumph intended - seals are not really needed.


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