Bearings and tappets

[skykrawler]

These are from the overhaul on my engine completed last August for those who have not seen this sort of thing.  This was an 1850 total time engine, so the original.  I believe there was a prop strike tear down 35 years ago (650 hrs) and they replaced the bearings while it was apart.    The airplane had very few hours on it the 4 or 5 previous year before I purchased it.

Edited December 18, 2022 by skykrawler
Typos

[N201MKTurbo]

That engine still had some life left.

[EricJ]

What was the oil analysis saying?    

I'd +1 that there's wear there, but nothing disintegrating.    The lifters look good, although the lighting on the one looks different.

It also looks like maybe they only replaced the front main bearing.   When the case is split they're supposed to all be replaced.

[A64Pilot]

I prop struck my Maule’s IO-540W1A5D at about 1900 or so hours, it had been prop struck before, so I decided to overhaul. Every single steel part met NEW tolerances, not serviceable, but new.

I feel sure that if an engine is TBO’d that most often very little money will be spent in parts, but if you wait until it starts making metal, your buying a whole lot of expensive parts.

That engine’s bearings are in such good shape because I bet they were replaced at the prop strike.

Lycoming has had for a very long time an SB that essentially has a list of wear items that your supposed to replace anytime you take the engine apart, as is a Factory SB insurence will pay for it, a prop strike can breathe a whole lot of hours into an engine if the SB is followed.

[Fly Boomer]

15 minutes ago, A64Pilot said:

I prop struck my Maule’s IO-540W1A5D at about 1900 or so hours, it had been prop struck before, so I decided to overhaul. Every single steel part met NEW tolerances, not serviceable, but new.

I think tolerances are important but, in my mind, NDT (magnaflux or whatever) on the crank and perhaps other parts is at least equally important.

[A64Pilot]

1 minute ago, Fly Boomer said:

I think tolerances are important but, in my mind, NDT (magnaflux or whatever) on the crank and perhaps other parts is at least equally important.

Yes, that’s the reason for disassembly. I believe the FAA  only requires some nut and it’s locking mechanism on the back of the crank to be changed and that nut can be changed without removing the engine. Probably prop flange run out too of course.

It’s Lycoming with its mandatory SB that requires removal and tear down and inspection, then another SB requires new bearings etc whenever an engine is disassembled.

That’s as of several years ago, things may have changed and yes of course tear down and inspection is safest and going back together with new wear items is smartest, but unless things have changed it’s not required. But as Lycoming has SB’s requiring both tear down and new parts insurence will pay for it.

The take away is unless things have changed, I’ve not researched a prop strike in quite awhile.

[jetdriven]

Lycomings have a requirement to Magnaflux or replace the crank gear at the end of the crank and also the lock tab and bolt. We stick new props on them and throw them back like that but we still send the engine for a teardown. Although Bill Cunningham at power Masters says all of these years doing teardown inspections he only had one crank that was cracked and that guy had sucked gear up early on takeoff and was running at full throttle, all the others  were landings or hitting something while taxiing, and he said none of those were broken.
But I try to tell the owners look, if somebody sees or suspects a prop strike and  it wasn’t torn down it’s going to cost you big time, plus also, every time they tear these things down the lifters are shot the cams are bad the bearings are bad this is your chance to really freshen it up and get it right. Also, make sure to specify the engine shop hones the cylinders  and puts in new rings, you would not believe this but one place I used just put them all back together and I just couldn’t even plus they were actually an expensive shop

[Fly Boomer]

1 hour ago, jetdriven said:

the others  were landings or hitting something while taxiing, and he said none of those were broken

Let’s start with the fact that you are a mechanic, and I’m not.  That said, my reading suggests that “broken” is easy to spot, but an invisible crack beginning to form deep inside the casting (or forging) isn’t.  I would be worried about experiencing the result of hidden damage in five or 10 years at an inconvenient moment.

[Guest]

I’m certainly no expert, but to me the crank bearings as shown above are worn out.  Most of the babbit is worn away exposing the copper substrate.

[skykrawler]

11 minutes ago, M20Doc said:

I’m certainly no expert, but to me the crank bearings as shown above are worn out.  Most of the babbit is worn away exposing the copper substrate.

The airplane is 40 years old.  I have no regrets about my decision. New Lyc cylinders.  I plan to have this airplane for a while.

[PT20J]

14 minutes ago, M20Doc said:

I’m certainly no expert, but to me the crank bearings as shown above are worn out.  Most of the babbit is worn away exposing the copper substrate.

According to Lycoming, its bearings are steel shells with three successive coatings: Copper, which  adheres well to the steel, then nickel to form a base for the final tin-lead bearing surface which provides lubrication during start up.  So wear can be determined by which layers are exposed.

[Guest]

4 minutes ago, PT20J said:

According to Lycoming, its bearings are steel shells with three successive coatings: Copper, which  adheres well to the steel, then nickel to form a base for the final tin-lead bearing surface which provides lubrication during start up.  So wear can be determined by which layers are exposed.

With copper being exposed, it suggests that several other layers are missing.  Old dirty oil full of nitric acid may account for some of it.

[skykrawler]

6 minutes ago, M20Doc said:

With copper being exposed, it suggests that several other layers are missing.  Old dirty oil full of nitric acid may account for some of it.

Coked up pistons, used oil excessively.  Ran great.

[Guest]

3 minutes ago, skykrawler said:

Coked up pistons, used oil excessively.  Ran great.

It just goes to show how amazing these antique engine are.  Still running well despite not being “perfect” inside.

[PT20J]

1 minute ago, M20Doc said:

It just goes to show how amazing these antique engine are.  Still running well despite not being “perfect” inside.

No kidding. I had a broken oil control ring that took out a chunk of piston skirt and ran metal through the engine. It was running great and we only discovered the low compression and metal in the filter and ring pieces in the suction screen at annual inspection. I don’t know how much longer it would have run, or how long it had been broken (somewhere short of 25 hours when the pre-purchase came up OK), but I was pretty impressed at its ability to soldier on though seriously wounded.

Skip