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Hi Chris - my engine was recently
overhauled, having fallen victim
to Lycoming's 'achilles heel' - their longstanding rubbing cam and
lifter design. At 600 hours, I found that the cam and lifters were badly
galled, with copious amounts of metal particles throughout the
engine. Frequent flying, use of oil additives, etc. are simply attempts to
stave off the real problem which is the rubbing cam and lifter design; the
solution is the new roller lifter design.
I left about 1/8" clearance between the molded
fiberglass seals and the aft side of the cowl air inlets to allow for relative
motion between the engine and cowl. Not the complete inlet seal that your plenum
design offers, but which shouldn't result in more than a miniscule amount of air
leakage. More importantly, I took action to seal wasteful air leakage
paths which rob cooling air from the all-critical cylinder heads.
Several years ago, I asked Lycoming what the
optimal CHT is and they simply said "the lower, the better". I estimate 320
degrees to be about the lowest obtainable, considering the size of our
air inlets. That's probably more than sufficient for the long term health
of the engine and attempts to go any lower would unproductively increase
cooling drag.
Yes, I'll be glad to measure upper plenum
pressures, let me know the procedure/equipment off list.
Respectfully,
Bill Rumburg
N403WR (Sonic bOOm)
----- Original Message -----
Sent: Tuesday, May 13, 2014 7:45 AM
Subject: [LML] Re: Cooler CHTs
Bill,
Is
that a new engine? -looks spotless.
Scott
Krueger was also able to get a really good seal on his baffles. In fact,
he had the highest measured pressure recovery I have seen using flexible
baffle material. You wouldn't happen to have (or be interested in
measuring) some upper plenum pressures for comparison? -forever in
search of cooling system data.
How do you interface to the
inlets? -any pics of that area?
thanks,
Chris
Zavatson
N91CZ
360std
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