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Thread: Lycoming O-290 C

  1. #1

    Lycoming O-290 C

    I am looking for an expert on old Lycoming engines. I bought and mounted a 1943 Lycoming O-290 C engine on my mostly finished Nieuport 28 replica. It has two #4370 slick mags, and I would like to put at least one impulse mag on the engine. Any thoughts or recommendations?

  2. #2
    FlyingRon's Avatar
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    I'm not sure that Slicks were ever officially approved for this engine though Unison does list the 4372 as fitting which as an impulse coupler. I'd put it on the left side as the mag switches typically have a left only starting option.
    Last edited by FlyingRon; 02-06-2017 at 08:45 PM.

  3. #3

    O-290 c

    Quote Originally Posted by FlyingRon View Post
    I'm not sure that Slicks were ever officially approved for this engine though Unison does list the 4372 as fitting which as an impulse coupler. I'd put it on the left side as the mag switches typically have a left only starting option.
    Ron, Thanks for the tip! Additionally, the engine does not have an engine driven fuel pump. I have installed an electronic fuel pump, but I feel fairly confident that I should have plenty of fuel head pressure at the carb from the gravity feed. Any insight into gravity fed O-290s...?

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    FlyingRon's Avatar
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    Got me. But I suspect you can treat the electric pump as a "boost pump" just in case. I'd be real concerned at full throttle applications making sure I was getting enough fuel though.

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    Dana's Avatar
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    Not to hijack this thread, but it's timely... I'm looking at a Starduster with an O-290G engine. My concern is that the compression is around 60/80 on all cylinders. Owner says it's been that way for the four years he's owned it with no change, about 5 hours per quart of oil. How concerned should I be? Otherwise it's a great deal (I haven't actually looked at the plane yet).

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    Quote Originally Posted by Dana View Post
    Not to hijack this thread, but it's timely... I'm looking at a Starduster with an O-290G engine. My concern is that the compression is around 60/80 on all cylinders. Owner says it's been that way for the four years he's owned it with no change, about 5 hours per quart of oil. How concerned should I be? Otherwise it's a great deal (I haven't actually looked at the plane yet).
    Where's the compression leaking out at?

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    Quote Originally Posted by Robert Mundie View Post
    Ron, Thanks for the tip! Additionally, the engine does not have an engine driven fuel pump. I have installed an electronic fuel pump, but I feel fairly confident that I should have plenty of fuel head pressure at the carb from the gravity feed. Any insight into gravity fed O-290s...?
    4-cyl Lycoming with a Marvel carb needs 1/2 PSI fuel pressure at the carb. Info may be found on line. That's where I found that info when I needed it five years ago. Doubt it's changed, but hey, verify it.

  8. #8
    L16 Pilot's Avatar
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    That's no doubt a bargaining point but as listed below it would be interesting to know where the leakage is going. It's not necessarily a compression test but rather the ability of the cylinder to 'hold air" at the top of the compression stoke. Going out the valves (though the intake or exhaust) that's one thing. Leaking into the crankcase is another and may be from the engine not being warmed up before the test is made. I've had engines that ran in the low 60's with the leakage test but would run 125 130 psi on a cranking test with the starter. Part of the problem is the engine is only in that position (TDC) for a micro second when the engine is actually running at speed. Plus the rings get a lot of their sealing pressure from high combustion pressure sealing the rings (especially the top) to the cylinder wall. Having said all this all cylinders running 60/80 "forever" might be a bit of concern and bears a more through look and you would also think there would be some indications of excessive 'blowby' out the breather tube i.e. oil on the belly. My .002 worth.
    If God had intended man to fly He would have given us more money!

  9. #9
    Dana's Avatar
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    Quote Originally Posted by L16 Pilot View Post
    That's no doubt a bargaining point but as listed below it would be interesting to know where the leakage is going. It's not necessarily a compression test but rather the ability of the cylinder to 'hold air" at the top of the compression stoke. Going out the valves (though the intake or exhaust) that's one thing. Leaking into the crankcase is another and may be from the engine not being warmed up before the test is made. I've had engines that ran in the low 60's with the leakage test but would run 125 130 psi on a cranking test with the starter. Part of the problem is the engine is only in that position (TDC) for a micro second when the engine is actually running at speed. Plus the rings get a lot of their sealing pressure from high combustion pressure sealing the rings (especially the top) to the cylinder wall. Having said all this all cylinders running 60/80 "forever" might be a bit of concern and bears a more through look and you would also think there would be some indications of excessive 'blowby' out the breather tube i.e. oil on the belly. My .002 worth.
    Hmmm, good point. There was some mention about not being satisfied with the performance of the breather catch bottle, so there's an indication it likely is rings / cylinders. If it truly is a quart in 5 hours it's not horrible (right?) or a safety issue... the price is right, so I'm hoping I could get it home and live with it for a year or two while scrounging parts for a top overhaul.

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    Quote Originally Posted by Dana View Post
    If it truly is a quart in 5 hours it's not horrible (right?) or a safety issue...
    No, that's not an issue.

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