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Thread: help with new used engine - where do I start?

  1. #1

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    Jun 2018
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    help with new used engine - where do I start?

    Just bought an 0-235 c1B. It came out of a colt in 2002. Log book shows just over 1600 hrs TT. Appears to have been removed for power upgrade and that is what I was told by the old guy I bought it from who said he witnessed its removal when he owned an avionics shop back in the day (2002). Who knows for sure, but thats the story. No Prop strike he insisted. non recorded in log. OK, so its as removed, with both mags.... except carb was removed, as was the ring gear.

    There was a thread from about a year ago that I followed. One thought that is prudent, is to consider it a core and rebuild it. The other, which is mine, is to determine if the engine is healthy and test run it statically. I have to buy a carb or use the new Rotec 40-3 tbi I have which sounds iffy compared to a $500 good used marvel schebler ma3pa. I also will replace the ignition wires, as they look rough and are consumable items.

    So, is there a way to determine if the cylinders need honing without removing the pistons and rings, in which case, it would then have to be done? If there is a little rust in the cylinders (I haven't checked yet), can they be "cleaned up" with a hone or overbored to be good?
    Is it necessary to break down the engine case to determine if the crank and camshaft are good or can I mount a dial indicator and verify that the crank is within tolerance and therefore ok. What must be replaced other than if there are AD items, since it sat for so long.

    I'm not a mechanic. I built one auto engine conversion with lots of help and understand how to do some things in a more generic sense.
    Please give me your experiences and opinions on apparently clean engines that have sat and whatever else you can to help me out.

    Eric

  2. #2
    CarlOrton's Avatar
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    Eric; That might have been my thread you read last year. I'm in the middle of rebuilding an O-200.

    Let me put it this way; if, every time you fly, and especially if you fly with a passenger, are you going to wonder if that crank really is good? If you're always thinking about it, does that really let you enjoy your plane?

    Dial indication alone is not the be-all/end-all to determining if the crank is in good shape. As an example, if there was a prop strike, on the Continentals the cam/crank gears usually suffer the most. Dunno about Lycomings. I don't care what your guy says. Unless you KNOW the plane, and you KNOW why it was removed, from firsthand contact and not hearsay, you have to treat it as an unknown. A static test run only tells you that it runs OK at that time. If there is a tiny stress crack, that will usually not show up on a test stand. Those buggers usually say Hi on a full power climb at full gross on a hot day - exactly when you *don't* want an issue. Yes, you have to split the case to get the parts which will have to be magnafluxed to specific test amperages, angles, etc.

    re: the cylinders, you can buy a very cheap borescope that works with your iPhone to check the inner surfaces. If there's light corrosion, you *could* remove and but 'em up a bit, but how would you know if the barrel is in spec, etc.? If you take them to a good shop, they're not going to want to just hone 'em. They'll want to do all or nothing, because trust me, ANYTHING that happens after that time and you'll be posting on here that everything was fine until THEY touched it. This is not unique to airplanes. Try and get an auto repair shop to replace ONLY the disk pads. They won't do it, because they then have no idea what other stuff might fail, opening them up to liability.

    That said, it's your plane. If you think it's a good engine and don't want to dig deeper, it's your well-being that's in jeopardy. Just don't hurt others, or others on the ground, but also don't give experimental aircraft a bad name.

    Last thought: If that engine has sat for 16 years, you (it) have issues.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  3. #3

    Join Date
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    Pullone cylinder or both on the same side and inspect the cam and lifters. If they are all ok and the cylinders are ok then assemble and run it. The oil pressure will likely alert you to any bearing problems. Check the oil filter at 5 hours and at ten hours. Change oil if all is good and agin at 25 more hours. Likely the cam is going to be rusted unless the engine was properly pickled. You will most likely need to overhaul it.

  4. #4
    cub builder's Avatar
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    Once upon a time I bought a "good used engine" that looked great on paper. 80 hours later that engine packed it in at night in the mountains.

    I've had one hard and fast rule for the last 31 years since that incident. I do not fly behind an engine on my plane until I have torn it down, done a proper inspection, and built the engine back up from scratch. The engine I bought for the last plane I built read much like your O-235 in the logs and according to the logs should have been a good engine as it was still on it's first run since new and was not run out yet. I decided to overhaul it anyway. What I found was all 4 cylinders had cracked heads, a cracked crankshaft, case out of spec and cracked, and a spauled cam. It cost me a bit more to overhaul it than planned, but I started out with an engine at 0 SMOH with all clearances meeting new specs and know exactly what I am flying behind. Look at as something that is likely to be a one time expense. Once it's done, it's done and it's unlikely you will ever fly enough hours to have to overhaul it again. Even if you do, the next overhaul will be many years into the future.

  5. #5

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    Any engine that has been sitting for 16 years and has 1600 hours on it needs to come apart. That isn't even a close call, especially if there is even the least bit of doubt about a past prop strike. Even if the crankshaft is straight there are other things that could be damaged by a prop strike. By doing a proper overhaul you can start off with a clean slate and a known quantity. You life is worth the cost of doing it right. If you are mechanically handy and have an engine shop nearby that will work with you it is possible to save some money by doing a lot of the work yourself.

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