Posted for "john wright" <n338l@gbronline.com>:

I notice in the Continental manual for the TSIO 550 that it states under the
topic of descent that cylinder head temps should not be allowed below 300
degrees for more than five minutes.  It doesn't address cruise operation
below 300 degrees.  I have the "Dolly Parton" cowling on my iv-p with the
large exhaust tunnels.  In the winter months most of my cylinders will run
below 300 degrees in cruise at most altitudes.  In the past I made some
winter baffles to decrease the diameter of my cowling inlet, which gives me
CHT's in the mid 300's in cold weather.  During annual we found what my A&P
said is uneven cooling resulting in hot spots on some of the cylinders
causing the oil ring to stick (unable to freely spin the ring by hand).  He
said it is not as simple as modifying the baffling.  He points out that the
way our intercoolers are set up that some of our cooling air from the upper
deck bleeds out by passing through the intercooler (by design) leaving less
to cool the cyl. head fins.  We replaced all six cylinders and rings at 772
hrs. and he is recommending not using the baffles this winter to improve
engine cooling.
    My question is: Does anyone know if it is harmful to run the Continental
TSIO 550 E1B below 300 degrees (usually in the 280-290 degree range) in
cruise?
John Wright iv-p