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

[tom paul]

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.

 

[Majorpayne317641]

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.

 

[andoman]

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…

 

[rockyfatcat]

Oil pressure and oil analysis. Compression is the biggie. Making metal is the concern.

TBO? It’s Just a suggestion for part 91. If its making compression and not making metal, fly it forever.