[xj-s] Valve Motion

["Kirbert" <palmk@mailer.gadcomm.net>]

It's not like this is a big revelation, or even has decent Jag 
content.  It's just something I realized recently, and thought I'd 
make sure everyone else realized it as well -- even though there's 
nothing they can do about it.

I have always kind of assumed that intake and exhaust valves, being 
circular, might rotate somewhat as the engine runs.  After all, cam 
followers or tappets seem to rotate -- their wear patterns confirm 
it.  It makes sense to me that valves being allowed to rotate a 
little bit might help keep their seats in good condition.

Fiddling with my valves, I realize now there's no way in hell they 
will ever rotate.  There is no positive anti-rotation feature, but 
the way the keepers are held against the valve stem by the spring 
collar means they ain't gonna move.  And the spring is pushing 
against the bottom of the collar at its top end and against the head 
at its bottom end.  None of those contacts are likely to ever "slip", 
so the only way the valve can rotate is for the valve springs to wind 
up -- good luck getting more than a degree or two of rotation out of 
that!

So: if one side of a valve doesn't sit on its seat quite right, it's 
gonna continue to leak and burn at the same place until the engine is 
rebuilt.  And any sideways load on the valve stem will continue to 
wear on one side of the valve and one side of the guide until they 
are both oval.

 -- Kirbert      |     If anything is to be accomplished,
                 |     some rules must be broken.
                 |          - Palm's Postulate

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