Thanks for the reply. This isn't normal wear. This
engine has excellent oil pressure, and there are no
indications of excessive heat in the cylinders. These
valves came off an engine that had probably 80,000
miles on it with no valve stem wear. That's why I'm
thinking it has something to do with the more radical
cam.
Regarding valve temps, I got a kick out of the price
of sprite exhaust valves (around $5). My Lotus valves
were $140 a piece (x16). They use sodium as a heat
transfer mechanism. A little slug sloshes out of
phase with the valve motion to transport the heat.
--- curt.onstott@orst.edu wrote:
> Ron-
>
> Exhaust Valves tend to wear faster because: 1) They
> get less lubrication
> because the pressure from the exhaust gas makes it
> harder for oil to make
> it's way down the valve stem. Since air is being
> sucked into the engine
> during the exhaust stroke, it is easier for oil to
> make its way down the
> valve guide.
>
> 2) Exhaust valves are subjected to high temperature
> exhaust gases. Intake
> valves are cooled by the intake charge.
>
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