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If I to a Top OH on a 1200 hour engine, How do I know when to OH the rest of it?

tom paul

tom paul

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It occurred to me that doing a top OH may make things seem better than they are down the road when there is a problem developing in the belly of the beast. Maybe a dumb question, and my simple answer is: look for metal. I don't fly my plane enough and I worry about can and lifter spalling. From what I understand, with oil analysis and filter cutting, one can see that issue if it happens, and deal with before catastrophic engine failure. I don't know what else to worry about. I am sure this is a well worn topic and I am excited to learn.
I know in the E-AB world, the hours and calendar limits are merely suggestions, but I don't want that leniency to get me into a dangerous situation.
Thanks for your thoughts.
 
I know people will disagree with me but the whole point of an overhaul at 2000 or any set limit is to open up the engine and check in on its health by inspecting and measuring components. A factory new engine may be able to go beyond overhaul, so can an engine that has been overhauled a few times, but once parts like the case and crank get through a few iterations of TBO things start to wear. The point is to capture this at TBO if possible and monitor it throughout the next TBO cycle. My engine came from lycoming in the 90s and it’s likely to have gone through a TBO or two before I got to it. My rods have been reconditioned and who knows how many hours they had before they were inspected and yellow tagged for me to buy. That’s why TBO is a way to check in on all of these items to make sure they are still ok to continue service. That’s my way of looking at it.
 
During the top end the lifters and cam can be thoroughly inspected. If they need attention then your concerns are moot.
Might as well remove the mags and eyeball everything you can inside the accessory case.
As for the bearings: How’s your oil pressure? If it’s steady and your pressure relief hasn’t needed to be adjusted all the way in to keep it in the yellow at idle and your oil analysis gives no hint of bearing wear then top overhaul and fly on.
I wouldn’t personally do a complete overhaul at 1200 hrs if it only needs a top and all indications are that it’s otherwise healthy.
For contrast, if the bottom end was shot at 1200 I would at least IRAN the top because it’s already apart and the added cost is reasonable.
Just my 2 cents.
Another question:
-how many years since the fuel system was overhauled? If more than 12-15 then there is cheap peace of mind to be had there.
-oh, and all the hoses, too if needed…
 
Foghorn said:
Why do you want to do a top overhaul?
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ECI-Titan nickel coated cylinders with 1200 hours. Oil turns black an hour after an oil change. Burning a quart every 90 minutes. No cross hatching on #4. Good compressions, and running strong. I did the oil control ring flush. Seemed to help a little but not a lot.
 
Dugaru said:
There is also reason to believe this is the safest approach, as it may well avoid forcing a functioning engine into the "infant mortality window" that accompanies overhaul.
Click to expand...
I hear this. But using a quart every 90 minutes by all accounts points to something needing attention I think.
 
If I understand Mike Busch’s presentations, you’re just as likely and maybe more-so to introduce problems during overhaul than you would for letting it run accepting wear beyond overhaul. If your scopes and oil samples are doing well, let it run.
 
There is no such thing as a Lycoming "top overhaul."

You're probably referring to cylinder replacement.

The way you figure out if the rest of the engine is out of time is the same way you always do if you don't replace the cylinders: Inspect the oil filter after each oil change, assess the quantity of metal contained therein. Lycoming Service Bulletin 480F is where you'll want to start.

- mark
 
Our 24 club planes with 360's average 1000 hours per year. We overhaul the cylinders at around 2500 hrs and do complete engine overhauls at 5000 hrs. Our engine guy says he doesn't find anything wrong with the bottom ends at the 5000 hour teardown but everything gets done. I would agree that if it's not making metal and compressions are good keep running it. We aren't likely to get as much out of an engine since we don't fly them enough.
 
Your question how do you know when to overhaul is pretty much the same, whether you choose to do the top end now and wait for the rest later… or do it all. If you pull a cylinder and see spalling and corrosion, the end is in need of overhaul, using a quart every 1.5 hrs. Mine uses. Quart every 6 hours.

Oil use, compression considerations, oil analysis all help guide your decision.

I’d pull a couple just and look at lifters and cam. If cylinders are not looking right… they may only need hone and rings… of course they may be shot…. Don’t know till you know.

It’s easy to remove cylinders in a day and go from there… if the rest of the engine needs to come off.. way easier to remove it with cylinders off..

Seldom is the time alone the governing factor.

Start with a cylinder or two and go from there.
 
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