O-200 Exhaust Valve

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Dugaru

Filing Flight Plan
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Aug 29, 2024
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Doug
So what do we think of this exhaust valve in a Continential O-200?

On the one hand, it looks like it has a good "burned pizza / centered target" sort of look. And I'm always looking for problems when none exist. On the other hand, the wide dark patch at the 2 o'clock position, and the two smaller, darker areas at the 7 and 8 (-ish) positions, looked different from the other exhaust valves.

Valve was not stuck, and spun freely in the guide (we did the "rope trick"). There was maybe (maybe) a little extra soot/carbon under the rocker cover.

valve.jpg
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Dugaru said:
So what do we think of this exhaust valve in a Continential O-200?

On the one hand, it looks like it has a good "burned pizza / centered target" sort of look. And I'm always looking for problems when none exist. On the other hand, the wide dark patch at the 2 o'clock position, and the two smaller, darker areas at the 7 and 8 (-ish) positions, looked different from the other exhaust valves.

Valve was not stuck, and spun freely in the guide (we did the "rope trick"). There was maybe (maybe) a little extra soot/carbon under the rocker cover.

View attachment 132891
a
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Looks like it might be starting to burn. What is the compression like in that cylinder? Can you hear leakage at the exhaust pipe?
 
That valve looks bad but small chance it might be salvagable? Mike Busch has a procedure to lap the valve in place. Then you fly the airplane for a few hours and check it again. That looks worth doing, maybe it can save that valve. If it doesn't and you must replace the jug, you haven't lost much effort trying.
 
MRC01 said:
That valve looks bad but small chance it might be salvagable? Mike Busch has a procedure to lap the valve in place. Then you fly the airplane for a few hours and check it again. That looks worth doing, maybe it can save that valve. If it doesn't and you must replace the jug, you haven't lost much effort trying.
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+1 for Mike Busch... I think you can find it on EweToob or EAA site
 
MRC01 said:
That valve looks bad but small chance it might be salvagable? Mike Busch has a procedure to lap the valve in place. Then you fly the airplane for a few hours and check it again. That looks worth doing, maybe it can save that valve. If it doesn't and you must replace the jug, you haven't lost much effort trying.
Click to expand...
If it's starting to burn, it's beyond lapping.
 
Might check for an induction leak.
 
I would try to lap it in place. See if you can photograph the actual seats. Fly for 10 hours and then re-do the borescope. Any persistent asymmetric heat signature or green deposits would have me very concerned.

What I don't see is a heat signature that reflects asymmetrical heating of the entire valve face. The "burned pizza" is relatively uniform. I think that's a positive sign.
 
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Many thanks to all. Time to gather more data and watch that lapping video!
 
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