Page 1 of 1

Exhaust valve problem options

Posted: Sat Feb 09, 2019 8:06 pm
by blsewardjr
During my annual this week my mechanic discovered that my #1 cylinder had a compression of 45/80 warm. Upon borescoping it he found that the exhaust valve was showing early signs of wear. Faced with pulling the cylinder to the tune of several AMUs, he offered the option of "lapping" it. The operation was successful, getting the compression up to 63/80 cold. We're going to look at it again in 25 hours. My mechanic runs a podcast on aircraft maintenance and I was the subject this week. If you're interested it's at http://airplaneownermaintenance.com/109 ... od-option/ Bernie

Re: Exhaust valve problem options

Posted: Sat Feb 09, 2019 9:00 pm
by waynemcc999
At my last annual, I had a burnt exhaust valve... decided to replace with a new full cylinder kit at cost of $1200 parts and a few hundred dollars labor. At the time the aircraft had 1800 tach hours and that was the first valve problem and therefore first cylinder replacement.

Re: Exhaust valve problem options

Posted: Sat Feb 09, 2019 10:23 pm
by Hans
How many hours on engine ?

Re: Exhaust valve problem options

Posted: Sun Feb 10, 2019 2:02 am
by blsewardjr
650

Re: Exhaust valve problem options

Posted: Mon Feb 11, 2019 1:56 am
by Pilot55
Usually the valve seat problem starts with valve guide wear. The valve now does not stay concentric with the seat and when the valve is seated does not make enough contact with the seat to pull the heat out of the valve. It also puts higher point loading on a smaller area of the seat and causes the seat and the valve to pound out in that area. The lapping will help for a period of time but if the seat is worn it will return.

Re: Exhaust valve problem options

Posted: Mon Feb 11, 2019 2:08 am
by blsewardjr
Bret- That what my research revealed as well so I had my mechanic check the guides. He says he didn't find any slop in them. That said, I agree that the problem will probably eventually return. Nonetheless I'm trying to follow Savvy's Mike Busch's advice to do whatever you can before pulling the cylinder. Busch believes that pulling cylinders can, if you're not extremely careful, result in much more serious engine problems. See
https://www.savvyaviation.com/wp-conten ... afraid.pdf Bernie

Re: Exhaust valve problem options

Posted: Mon Feb 11, 2019 2:53 am
by ZAV
That was a scary article.