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Top Overhaul

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Quick history, February 2008 MOH with New Lycoming Cylinders. September 2012, TSMOH 661, metal found, removed engine and found bad cam. New cam, lifters, bottom end, gaskets, bearings, case flush etc…Cleaned cylinders, back in service.

About 1 1/2 years ago, started to use a little more than the usual 1qt every 10 hours, more like 1qt every 7 hours. Noticeable oil on the belly and out the breather tube. 1 year ago, installed an Airwolf to catch residual. Okay for the most part, but oil usage continued to rise, but not consistent. Oil analysis still good, no significant changes with the trend.

Now staring to rethink things, stuck or broken oil control ring or maybe worn valve guides. Beginning of October, did the Savvy/ Busch ring flush, definitely stirred up some sludge. After a long flight this past late October, fair amount of oil out of the Airwolf breather hose (supposed to just be condensation) onto the belly. Figured that the hose was caught up in some sort of suction and drew it out of the case. Repositioned tube, still an issue. Managed to catch a piece of debris in the check ball for the oil bypass leading to an interesting oil pressure issue! Cleaned the check ball and seat, back to normal oil pressure.

Current status. TSMOH 1837, Time since bottom end, cam and lifters 1175. Engine was running fine, no power issues at all, just a couple black oil fouled plugs and oil usage up. Borescoped all cylinders and didn’t see any real issues, just some oil pooling and a few vertical scratches, nothing significant.
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Most engine shops are 3-6 months out on an entire overhaul plus some additional time for parts availability issues. My engine shop can turn my cylinders around in less than 2 weeks for me if they spec out okay and don’t need to be nickel plated.

Pulled all 4 cylinders off yesterday and found the 2 rear pistons a little oil cooked? Not sure what else to call it. #3 oil ring barely moved and has a significant amount of crud. #2 piston looks a lot like new! Good cross hatch still visible in all cylinders and the valves look like they should. Engine shop agreed that that the only way for that case pressure and blow by is rings.

Planning forward. Overhaul all 4 cylinders, replace everything that is 1837 hours old. Oil cooler, mechanical fuel pump, overhaul right Mag (left is Surefly and only 300 hours old), oil cooler lines (D style), all fuel lines and temp control oil valve. This should buy me 700-1200 hours and then pull it or exchange it for new or overhaul.

Any comments or suggestions? Here are a couple shots.

Thanks,
Dave

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