O-435 cooling issues...

T

trombair

New member
greetings!

vic steelhammer & N522A here.

anyone have experience with taming the CHT's on the #3 & #5 jugs of an O-435-A? since installing an engine anylizer in Feb., i've been scaring myself to death looking at the CHT's on the rhs of the engine in cruise. climb @ 85-90mph is ok with all temps below 390degF, but in cruise w/ cowl flaps closed and lightly leaned, #3 & #5 readily go over 420degF. :shock:

i've done all the usual stuff; sealed the plenum box, inter-cylinder baffles are tight, no induction leaks, even swapped probes but nothing seems to work. i've corresponded with jon barron and jan gerstner and spoken with the factory folks and tom witmer-no one seems to have any good concrete solutions. i'm stumped!! :?

my thoughts are that there just isn't enough exit area for good scavenging of the low pressure side of the plenum. i can imagine a new lower cowl with more exit area, no cowl flap and a lip akin to the arrangement on a cruiseair might help. but before i go to the trouble of building such a thing i thought i'd check with the operational experts in the field.

so, any and all thoughts are most appreciated.

here's to cooler heads!

blue skies,
vic & N522A
 
Take a very close look at the cylinder head castings. I read recently about an airplane having cylinder heat problems, and it turned out that the head fins still had some casting flash between them. Cutting/filing that flash out reduced the temps to normal.
 
hey roger!

good thought, but i must have seen the same article about the cylinder head castings and checked it out first thing. they're all ok, tho.

i think i may try removing the "venturi cowl" that's attached to the firewall and see if the extra area contributes to better scavenging. hope to fly it on saturday. will let you all know.

blue skies.
vic & N522A
 
My 14-19 never came with a "venturi cowl" I have no problems with high cht"s. I usually cruise with the cowel flaps fully closed even on hot days.
 
hey mark!

thanks for the feedback!

do you have good instrumentation on your engine? i wasn't too concerned either, until i installed the 6 point EGT/CHT engine analyzer and saw what was REALLY happening up there! :shock:

i have corresponded with jan gerstner on this topic and he says he went thru all this with his 14-19. he found that about 1/2 of the 14-19's he polled had a CHT problem and 1/2 didn't. it would be interesting to know what kind of instrumentation went with each of those "data points".

i flew N522A last weekend without the "venturi cowl" and it didn't make any difference in CHT's. my next move is to fabricate a "lip" on the lower bowl (similar to the cruiseair) to try to improve the scavanging in the low pressure side of the plenum.

i'll post my findings soon!

blue skies,
vic & N522A
 
I am a relatively new Cruisemaster owner and I had a JPI installed on my O-470. I was appalled at the CHT on the #4 cyl. When I flew it out from California to Texas the ambient temps were in the low 100s and I would see 450 or more right after takeoff. Of course, a short fuel stop on a hot day is going to give you the toughest test.

I found that the rubber gasket on the baffling was down about a quarter to a half inch from the top of the cowling. When I re-aligned it the #4 temp went down about 35 degrees.

If I hadn't had the JPI installed I never would have seen the problem, since the factory probe was on a different cylinder (#6 I think) and the other cylinders were OK.

Of course, that's on a 470 and the 435 may have different issues.
 
You must log in or register to reply here.
Back
Top