I'm not an expert but if a Vanagon motor got that hot you would be in
catastropic failure big time.  I have seen motors that got hot enough to drop
valve seats in the waterboxer but they didn't get hot enough to damage the
steel parts of the motor (or even the aluminum ones which would go first).  No
flame intended.  I know with my aircraft background I confuse waterboxer
problems with aircraft engine problems too.
Ken Wilford
Van-Again
John 3:16