Engine roughness

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AKar
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Re: Engine roughness

Post by AKar »

Oracle427 wrote:An exchange engine from the factory for an overhauled unit. We contemplated rebuilding ours that served us well for 2400 hours (SNEW) The "new" one came to us with 4400TT.
Yea, the last one seemed to be a good one. Hopefully this ends up being one as well, your experience rolls the ball towards ovh not being the best success they've done.

-Esa

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Oracle427
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Re: Engine roughness

Post by Oracle427 »

Two new cylinders went in and I took the bird up for two and a half hours to run the engine hard and break them in.

I had a look ash the old cylinders before they go back to Lycoming. The exhaust valves have nice bullseye patterns in both cylinders and no discoloration on the edges of the valves. We haven't a clue why they failed.
Flight Simmer since 1983. PP ASEL IR Tailwheel
N28021 1979 Super Viking 17-30A

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AKar
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Re: Engine roughness

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Yeah, the burn patterns are not linked to the sticking issues in any too direct way, I understand. The sticking mostly comes from the Lycoming's design running the stem area hotter than the design can do, it appears, and the QC I'd argue. A perfectly seating valve face can stick very well. I'm hardly knowledgeable in this area, as I've studied it very little because we had no this kind of issues around here in the engines I followed.

Any asymmetrical burn pattern on the face, such as:

Image

..gives an indication of a valve face failure, or of a poor sealing on some edge (the latter often giving a result of the former). Albeit this specific example appears to have some evidence of detonation as well, maybe having caused the valve failure in the first place, but regardless!

-Esa

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Oracle427
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Re: Engine roughness

Post by Oracle427 »

Yes, understood that sticking is not directly related to poor seating either by improper QC or operation.

All the shops I have discussed this with feel it is highly unusual that sticking would be an issue at only 100 hours and 400 hours on the two cylinders in question. Even Lycoming doesn't expect that type of issue to develop that often.
Flight Simmer since 1983. PP ASEL IR Tailwheel
N28021 1979 Super Viking 17-30A

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AKar
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Re: Engine roughness

Post by AKar »

And that would bring this back to my initial pessimism:

Anything can go wrong with these engines, at any time,
for any reason
! :mrgreen:

These can be, and are, understood in the tech side, but the field is a mess. Everyone's afraid of the ball, for catching it would mean responsibility.

-Esa

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Oracle427
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Re: Engine roughness

Post by Oracle427 »

Here's the break in flight. Hand flown for 2.5 hours over the "onion fields" of Warwick, NY. :p~

It was very interesting seeing how my TIS-B traffic failed to pick up so many aircraft doing flight trainig in the area. I had to modify my pseudo racetrack several times to avoid maneuvering traffic that I could only monitor visually. It was the first time I got to watch an aircraft stall so many times in a row! :)

Image
Flight Simmer since 1983. PP ASEL IR Tailwheel
N28021 1979 Super Viking 17-30A

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