Steve Pierce
BENEFACTOR
Graham, TX
So helping my buddy Travis with the annual on his Pacer and on the compression test we had cylinder #2 that was 60/80 and #4 was 40/80. The cylinder that was 40/80 got replaced with new about 4 years ago and the 60/80 was the same last year. Both were leaking out of the exhaust but the valves looked good through the borescope. Tried running it up again, staking the exhaust valves and no change. Got out the wobble test fixture and found both exhaust valve guides worn beyond limits. Looked at the rocker arms and the rocker arms with the oil squirters that should pump oil onto the hot exhaust valves were installed on the intake valve. Cause found now to fix. Pulled the two cylinders and it was obvious that the exhaust valve guides were way loose. Travis took the cylinders to Sal's cylinder shop for new guides. The newer cylinder was no issue but the older cylinder had a small crack in the exhaust port so bought a new one to replace it and another to replace #1 which was an older overhauled cylinder since #3 and 4 had been replaced 4 years ago, now we have 2 new and 2 cylinders with only a few hundred hours since new on a 600 hour engine. Should be good for years to come. All we have to do is put everything back together and start planning a trip to Idaho in a few weeks. Ha. Get the cylinders on and it feels kinda tight. Hmm, what the heck. Text Ken at LyCon to see if he has seen this before. In the meantime we back the torque off the front main, still tight. Back the torque off one nut on the center main and the crank spins like I am use to. About that time Ken calls me and explains that the crankcase has fretted and we just torqued it back to spec and took out that extra clearance that had fretted away. Was hoping for a magic fix but there is none. Reviewed the logs and found all the yellow tags from the last field overhaul but nothing about the crankcase. Nothing in the logbook entry as well, not sure about the overhaul before that. Conclusion is that the engine needs to come off, case split, crankcase sent out to have the halves milled and mains and cam bores bored. Luckily I have an overhauled 160 hp narrow deck crankcase stashed for one of my cores so we won't have to wait for the case to be overhauled but another lesson learned. Travis was researching last night and found this issue referenced in Gordon's thread when he found a crack in his crankcase. https://www.supercub.org/forum/showthread.php?53815-Cracked-O-320-Case-Best-way-to-proceed/page2
I like to say I will know it all when they start shoveling dirt on my face, just another case of something new learned. Now to get to work so we can do some fun flying. Just thought others might like to log these lessons away for the own use down the road. Big thanks to Ken at LyCon for his insight and willingness to share his wisdom with me over the last 20 plus years.
I like to say I will know it all when they start shoveling dirt on my face, just another case of something new learned. Now to get to work so we can do some fun flying. Just thought others might like to log these lessons away for the own use down the road. Big thanks to Ken at LyCon for his insight and willingness to share his wisdom with me over the last 20 plus years.