Re: Uncorked exhaust - warped valves

[Doug Rasmussen <DougRasmussen@domain.elided>]

Message text written by Ted Borck
>If the exhaust pipe is short enough to allow [relative] cooler air to
reach the *hot* exhaust valve(s), the exhaust valve may warp.

A warped valve will not seat properly.  Valves (especially exhaust)
are cooled by heat transfer upon intermittent contact with the valve
seat.  Sodium is also used (in high output engines) to [internally]
cool exhaust (and sometimes intake) valves.

The portion of the exhaust valve face which doesn't contact the valve
seat will not be cooled by contact with the [relative] cooler valve
seat and thus burn in that area.

Once *hot* exhaust gas blow-by occurs in the area not contacting the
valve seat, the situation gets progressively worse<

Ted,

  This is a very logical explanation, but do you REALLY know that valves
warp because of exposure to the cool air or are you just speculating that
it may happen?  I'm curious about your source of info since I've been
hearing about warping and burning valves for years and wondered if it was
any more than a myth.

Thanks,

Doug