semerson
Well-Known Member
- Joined
- Aug 5, 2017
- Messages
- 140
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So, about a month ago, I flew from my home base in Glendale, AZ to Eugene, OR and back over a weekend in my 1964 Cherokee 235. On the return trip, about 5 miles from my home base, as I pulled back the throttle to descend 1000 ft to get to TPA, my engine suddenly started shaking violently and tried to continually die on me. I contacted the tower to let them know of my situation and that I was inbound. (I did not declare an emergency, and looking back, I should have)
As I flew her in, I could see the wings visibly shaking with the engine vibrations and the engine was constantly battling to stay alive. I landed and was able to taxi to the ramp and shut her down.
A few days later, I was able to get my mechanic to take a boroscope to the inside of what we determined to be a bad cylinder #2 (absolutely no pressure retention when the prop cycled). We believed it to be a stuck exhaust valve, but when we looked with the scope, the entire interior of the cylinder looked like swiss cheese with all the gouges out of the cylinder and piston head. We looked where the exhaust valve *should* have been only to find that the entire exhaust valve head was missing and all that remained was the stem.
Has anyone ever experienced an entire exhaust valve head disintegrating and gone missing? I've seen little chunks lost, but I (and my mechanic) have never seen an instance of the entire valve missing.
I am not entirely sure what would have caused this. The engine has about 700 hours since its last overhaul, but that was performed nearly 40 years ago (previous owner did not fly much but aircraft kept in Arizona). I operate about 25 degrees EGT ROP and I usually operate at about 55 to 65% while flying. I had about 50 hours on the airplane since the last annual, which included an oil change.
I'm relatively new to ownership and am interested to see if there is something that I should be doing differently in how I fly her.
As I flew her in, I could see the wings visibly shaking with the engine vibrations and the engine was constantly battling to stay alive. I landed and was able to taxi to the ramp and shut her down.
A few days later, I was able to get my mechanic to take a boroscope to the inside of what we determined to be a bad cylinder #2 (absolutely no pressure retention when the prop cycled). We believed it to be a stuck exhaust valve, but when we looked with the scope, the entire interior of the cylinder looked like swiss cheese with all the gouges out of the cylinder and piston head. We looked where the exhaust valve *should* have been only to find that the entire exhaust valve head was missing and all that remained was the stem.
Has anyone ever experienced an entire exhaust valve head disintegrating and gone missing? I've seen little chunks lost, but I (and my mechanic) have never seen an instance of the entire valve missing.
I am not entirely sure what would have caused this. The engine has about 700 hours since its last overhaul, but that was performed nearly 40 years ago (previous owner did not fly much but aircraft kept in Arizona). I operate about 25 degrees EGT ROP and I usually operate at about 55 to 65% while flying. I had about 50 hours on the airplane since the last annual, which included an oil change.
I'm relatively new to ownership and am interested to see if there is something that I should be doing differently in how I fly her.
