Posted for "George Braly" <gwbraly@gami.com>:

 Dom,
 
 If you read a bit further in Lycoming's materials,  including the
 material referencing the 435dF upper limit,  you will see that they also
 recommend normal operations at or below 400d F.
 
 There is a lot of accumulated recommendations by OEM's for temperatures
 in that range.
 
 There is a lot of good, well controlled, recent, experience that
 supports numbers in the 380dF range and not exceeding the 400dF range on
 a routine long term operating range.
 
 There is also a lot of good experience that operations down as low as in
 the 290 to 320dF range works well, also.
 
 In fact,  there is VERY strong evidence that operation of TCM engines
 down as low as 240dF works very well with absolutely minimal blow-by due
 to piston/barrel dimensional fit issues.
 
 That comes from the fact that one TCM engine that uses the same barrels
 and pistons and rings and valves as the others, operates at 240dF, by
 design.
 
 Regards,  George