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Q: I recently bought a 1984 Maule M7 with a Lycoming IO-540 engine. I have about 50 hours on it and it has been running quite well. I have a six-place EGT/CHT.
Recently I flew for a couple hours and after a few hours stop went to fly again and saw that the #5 EGT/CHT were both very low and the engine was running rougher. It got better as things warmed and I flew back. The next morning it was the same.
Compression and plugs are both good. I suspected a sticking valve. I pulled the rocker cover on 5 and found the outer exhaust spring broken into three pieces. I pulled the other covers and found another exhaust and an intake outer spring broken low, but in only two pieces.
The top has 1,400 hours on it, 500 on the bottom. I am replacing all of the exhaust and intake springs and reaming all of the exhaust guides. Halfway through and not a hint of drag on the valves yet. Is there something other than sticking valves that would have caused the breaks? Fatigue maybe?
Lycoming 540 engine.
A: Now here’s an interesting subject that I haven’t heard about in probably 50 years. However, I’m going to guess that it may still be caused by the same condition today that caused it to happen so many years ago.
The common report back then was that at just about lift-off the engine would lose maybe a couple hundred RPM, but continue to operate somewhat normally with maybe a little roughness. As you experienced, the next flight of the day would be perfectly normal with no indication of the symptoms observed on the first flight. At the time, those of us at Lycoming gave it a name called “morning sickness” since it usually occurred on the first flight of the day.
Even though the total time on the engine is 1,400 hours, if you do the math, that means it’s at least 36 years old.
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