[TR] Valve cover gasket TR3

[Geo Hahn]

I have always used the cork and have reused them through many many
valve adjustments.  I note which way is forward & up and reinstall it
with the same orientation and, of course, do not over-tighten.  Over
time it has taken on a shape to accomodate the edge of the valve cover
making it molded custom cork of a sort.

Note that there are different cork gaskets on the market -- looking at
a couple of spares hanging on the pegboard (one quite old & one left
over from a gasket set purchased mainly for the manifold and head
gaskets) I see that one (Payen?) is quite a bit thicker than the
other.

I do not doubt that the silicone is a fine product -- just noting that
the cork can work fine for some.