Steve Pierce
BENEFACTOR
Graham, TX
So I participated in the STOL Demo at Oshkosh and had a lot of fun. I noticed that my engine started to hesitate a bit when i pushed the throttle forward on take-off so when I got home, like I did prior to going to Oshkosh I changed my oil and checked my compression. Cylinders 1 through 3 were all 76-78/80 like they have always been over the almost 5 years I have owned my super Cub. However, the best I could get on cylinder #4 was 58/80 with the air coming out of the exhaust. Borescope showed everything looked normal. I flew the airplane around the pattern a few times and staked the valve but still no change. I recently realized that I was just putting the tach time in my engine log when I changed the oil and checked compression and I better total up the time since major overhaul. After all I have had it almost 5 years and it had almost 1600 hours on the factory overhauled engine when I bought it. Well after I totaled the numbers a few times I realized I have 2124 hours on the engine and it still only burns a quart of oil every 10 hours or so and all I have had to do was general maintenance on it. When I pulled the rocker cover to stake the exhaust valve I could see where it looked like combustion gasses had been getting into the rocker cover area so I got out my valve wobble test fixture and printed off Lycoming Service Bulletin 388C. Well low and behold I had a little over .050" of clearance vs the service limit of .030" Lycoming says I should have. Mystery solved, major dilemma started.
Once I knew the issue and how much time was on the engine etc I had to start seriously thinking about my options. Now we are talking some serious dollars for a complete overhaul and not chump change to top it. I gave Ken Tunnel a call to see what he thought. He figured I'd find a bad cam and lifters when i pulled a jug until I told him it was a roller cam engine. I also pull the filter and check it regularly and know it has been clean. He said other than the top end that is usually the only thing he finds wrong on an O-320 with these times. Kinda my experience as well although he sees way more engines than I do. So now what? Buy 4 new cylinders and top it, get these 4 rebuilt since they are first run cores, put a guide in this cylinder and keep going, install the narrow deck engine I have until I can do a complete overhaul? Sell it and get a less expensive hobby? :lol: Decision, decisions, decisions. Exploring my options$.
Once I knew the issue and how much time was on the engine etc I had to start seriously thinking about my options. Now we are talking some serious dollars for a complete overhaul and not chump change to top it. I gave Ken Tunnel a call to see what he thought. He figured I'd find a bad cam and lifters when i pulled a jug until I told him it was a roller cam engine. I also pull the filter and check it regularly and know it has been clean. He said other than the top end that is usually the only thing he finds wrong on an O-320 with these times. Kinda my experience as well although he sees way more engines than I do. So now what? Buy 4 new cylinders and top it, get these 4 rebuilt since they are first run cores, put a guide in this cylinder and keep going, install the narrow deck engine I have until I can do a complete overhaul? Sell it and get a less expensive hobby? :lol: Decision, decisions, decisions. Exploring my options$.