REFLECTOR: CHT too cool

[Chuck Jensen]

Cylinder head temp problems are not unusual, but I have a different twist.  My CHT's are too cool.  I can only recall once or twice that a cylinder head ever got to 400F.  Most run 350F to 390F during hot, hard climbs, but at cruise, and running lean of peak, it's not unusual for 2 to be below 300F and the rest just barely over 300F.  
 
Now, it well known that engines are most efficient at higher temps and I believe Lyco's recommendation for an IO-540 K1A5 is CHTs in the 375F to 400F temp range.  This would also seem to imply that I'm suffering unnecessary cooling drag from overcooling the CHs.  Oil temps at cruise are 195F-200F but will rise to 240F during long climbs.
 
So, my question is, 'is there a way 'adjust' cooling to CHs' that may reduce drag by reducing inflow through the overhead NACAs for downdraft cooling, without sending the CHTs too high during climb or aggravating oil temps during those climbs as well?

Chuck Jensen 

 

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