My 0-200 was installed in 1971 and the lower lip has never been on. Off hand, I don't know whose STC it is installed under (I should know this by now ) so I will have to look it up. Strange as it is, I can't get my engine to run warm enough sometimes.
I am looking at the parts book, that lip is part of the "sumerization kit" and looks to be held on by 11 PK76 sheet metal screws - so it could come on and off with the seasons...
I want to be the last guy to fly across the USA with no radio
The part number I come up with is 052199 Lip-Cowl This is on page 133 and 134 of my original parts book. There is a doubler on page 69, part No. 0452208.
Most of the '47 up cowls that I have laid eyes on around here do not have any lips, just the doubler.
I want to be the last guy to fly across the USA with no radio
Here is the picture of the part number called for in STC SA547EA. It is called for in the late serial number airplanes in the manual but is to be added when the O-200 is installed. The STC was originally for the 140A and the Model 120 and 140 were later added. Depending on the cowl on your airplane the shape will be different. I have flown long days in the summer prior to installing one and the temperatures definately dropped with the doubler. I have blocked the blast tube also and noted increased temperature and decreased oil pressure with out it.
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A&P IA. Holder of STC for O-200A's in 120, 140 & 140A's. Engine overhauls on C-85's ,C-85's with O-200 crankshaft, C-90's and O-200A's
State Rep for California
If you peruse your parts manual, you will find the lower cowling lip design under the options section called the summerization kit. It appears to have been simply screwed on...
It is my understanding that the 0-200 muffler pipes face forward because the 0-200 cam has more overlap and the forward facing pipes provide more back pressure. I would keep them sideways or facing the rear on c-85's, maybe even early C-90's. Forward facing pipe openings might cause a leaner mixture on C-85's. I have left mine (C-85) long to get the exhaust and noise away from the airframe.
Dave Spur said his CHT was low to mid 200's on the front left (#2?) cylinder. I have checked top and bottom temps using a spark plug bayonet on the rear right (#1) and find that the top plug measures 300 all the time but the bottom runs about 350 and goes higher with leaning and flight conditions, etc. Mine are Superior cylinders which have better cooling fins around the exhaust port and nearby plug than the Continentals.
Actually, that is the rear left cylinder. Attached are pics of my 0-200 installation, lo and behold I have a sort of forward/sideways facing pipes. I also have a doubler on the inner lip of the lower cowl (early Style) but no sign of screw holes for the summerization extension. Still, runs pretty darn cool.
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Dave Sbur/Vancouver WA
N110V C-140 #8748 Member#6597
Asso. Rep. Washington State
Learn from my problems-it's cheaper!
The 150 type muffler provides back pressure due to its baffled construction. The cut on the exhaust out pipes is a matter of preference.
I see Dave's are cut to follow the lines of the cowling. My 120 with with 150 Mufflers if the same way. My 150 with 150 Mufflers has them cut off with no rake at all. The 1947/48 140 Illustration has them square cut or slightly tilted back.
I'm not sure there is one right answer.
A&P IA. Holder of STC for O-200A's in 120, 140 & 140A's. Engine overhauls on C-85's ,C-85's with O-200 crankshaft, C-90's and O-200A's
State Rep for California
My experience is with 150's and not 140's, so take this with a grain of salt. On 150's, the O-200 exhaust system stack openings are supposed to follow the cowling contour (facing forward), and only stick out an inch and a half or so past the cowling (the 140 cowling is smaller, I think). They have been flown on 150's for years reversed, with no adverse affects that I know of. I would think the STC for 140's should specify the correct mounting.
As for cutting the pipes, I wouldn't. The length and diameter of pipes in some applications "tunes" the pipe for better scavenging at max operating rpm for that particular engine displacement. This proper scavenging helps keep cylinder head temps down, and all piston engines need some scavenging, otherwise power output and cooling suffers. Having the stacks reversed should affect the tuning and scavenging (due to back pressure changes) but doesn't seem to have that much affect on O-200's. I suspect that the stacks are so short already on O-200's, that the "tuned" rpm is too high to be obtainable with a normal prop. This may have been an intentional compromise for noise purposes, as a well tuned exhaust can "bark" at you (like a 351ci Boss Mustang). If this is true, the O-200 exhaust installed on a smaller engine would be farther out of tune due to the smaller displacement. Shortening the stacks would aggravate this still further. There are a lot of "should's, could's" and "suspicions" above. As I said, take it with a grain of salt, but it is something to consider.
As for the lip at the bottom of the cowl; It sticks out into the normal airflow on 150's and others in order to create a low pressure area behind it in the cowl opening. This low pressure area helps "pull" the cooling air through the engine and out. Engines run best and last longer at the normal operating temperature they were designed for. If your engine is already operating within the proper range, it is possible to make it run too cool by improving the cooling too much, particularly in cooler climates. This may be why one previous owner did a temperature study on his airplane. 200° - 250° cht is unheard of in cruise flight in a 150, and I think that is too low for cylinder longevity. 300° - 325° I believe is more normal, but I need to confirm this. The ideal cooling system will of course have similar cht's on all cylinders.
) so I will have to look it up. Strange as it is, I can't get my engine to run warm enough sometimes.