CAM LOBE CORROSION AT PREBUY?! A DULL TALE OF 1200 HRS SAFE LYCOMING OPERATION

[PT20J]

Lycoming 4 cyl engines have 8 valves and 6 cam lobes, so two lobes actuate 2 lifters each. I wonder if those go out first?

[EricJ]

12 minutes ago, 201Steve said:

Gotta go dipstick tube.
Put a group of engineering students together, with all of their materials and tools, offer a grand prize of a couple thousand bucks, making a tiny camera do a 180 and telescope a little further up wouldn’t be asking the impossible. I’ll throw down some prize cash. 

It's a very tough ask, because even if you do manage to make the sharp turn and make it up through the drain groove, you still have to find your way around the crank, counterbalance weights, and pushrods to get up to where the camshaft is.  Then you have to maneuver around to see the various cam lobes.  It's not really very practical, imho.   

[PT20J]

Send me the two thousand bucks and I’ll see about it 

[Kelpro999]

1 hour ago, 201Steve said:

do a 180 and telescope a little further up

 And after that , go around the crankshaft up to the top from one end to the other. 

[201Steve]

Arghhh was t thinking about the dipstick tube going right into the oil pan (duh). Gotta then get thru the little gap yeah…  how about breather tube outlet where does that go
 

 

[201Steve]

Be real cool if you could just have a gosh darn inspection hole somewhere on top of the case threaded in. 

[PT20J]

Just get DLC lifters and a new camshaft when you overhaul and forget about it. 

[jetdriven]

8 hours ago, 201Steve said:

Arghhh was t thinking about the dipstick tube going right into the oil pan (duh). Gotta then get thru the little gap yeah…  how about breather tube outlet where does that go
 

 

Into the accessory case.  

[AJ88V]

What we need is some of them nanbots to inspect the camlobes.  Keep reedin' bout em in the magazeens.  Heck, them nanbots could probly even repare those camlobes and fix other sh!t while we're flyin. Bout time aviation caught up with the modern world!  Whare's Elon when we need him?

[Jsno]

On 1/22/2025 at 9:30 AM, AJ88V said:

There's no way I'd allow a cylinder to be pulled for a pre-buy.  Just move on.

Think I know the answer to this, but asking this because I read the Mike Busch columns in AOPA where shops do unscrupulous things....

QUESTION:  Let's say you're selling your plane and you've just completed annual with a shop you've used for years.  The potential buyer has a pre-buy done by a mechanic of their choice.  Can the A&P performing the pre-buy inspection ground the airplane if they find (claim) a discrepancy?

I imagine this could turn very ugly.

 

All the A&P can do is give a list of discrepancies to the owner and document any maintenance actin that he has done in the log book such as “removed filter and inspected, found eraser head size amount of ferrous metal in the filter. 

[201Steve]

11 hours ago, PT20J said:

Just get DLC lifters and a new camshaft when you overhaul and forget about it. 

Yeah, when I dropped off my engine for overhaul (the second one after Jewell’s horrendous work) I said do whatever you do but I want Lycoming lifters and cam. After I flew it home and started going through all the paperwork, I noticed a superior part number living near the line items “cam shaft” and “tappets”. You can’t win for losing sometimes. 

[201Steve]

1 hour ago, AJ88V said:

What we need is some of them nanbots to inspect the camlobes.  Keep reedin' bout em in the magazeens.  Heck, them nanbots could probly even repare those camlobes and fix other sh!t while we're flyin. Bout time aviation caught up with the modern world!  Whare's Elon when we need him?

A bee sized drone to zing in there and have a good look around. 

[201Steve]

11 hours ago, PT20J said:

Just get DLC lifters and a new camshaft when you overhaul and forget about it. 

You know what’s interesting and I’m sure you’ve seen discussed before as I have, this wasn’t such the problem for a long time that it seems to be now. Friend of mine has a Cessna cardinal (same engine) overhauled in like 1995, in coastal environment, no issues. 

[jetdriven]

12 minutes ago, 201Steve said:

Yeah, when I dropped off my engine for overhaul (the second one after Jewell’s horrendous work) I said do whatever you do but I want Lycoming lifters and cam. After I flew it home and started going through all the paperwork, I noticed a superior part number living near the line items “cam shaft” and “tappets”. You can’t win for losing sometimes. 

The engine shop cut your engine life in half.  But at least they saved 50$.  
but seriously I put this in writing and verify it before taking delivery. It’s that important. 

[philiplane]

13 hours ago, 201Steve said:

Gotta go dipstick tube.
Put a group of engineering students together, with all of their materials and tools, offer a grand prize of a couple thousand bucks, making a tiny camera do a 180 and telescope a little further up wouldn’t be asking the impossible. I’ll throw down some prize cash. 

It's not possible to make the three bends required to get through the dipstick opening, the case halves, then around the crankshaft, to reach the camshaft.

Even if it were, by the time you got to the cam, the lens would be smeared with oil.

[Yetti]

Do you have an approximate manufacture date of the cam and lobes?    I am still holding to the theory that the 1990s cams/lifters had bad metallurgy.     

[hammdo]

15 hours ago, PT20J said:

Lycoming 4 cyl engines have 8 valves and 6 cam lobes, so two lobes actuate 2 lifters each. I wonder if those go out first?

Mine did, plus the 2 around them. The cam and lifters were ground and certified last IRAN. This time, new cam and DLC lifters, etc on this new IRAN…

-Don

[MattCW]

3 hours ago, philiplane said:

It's not possible to make the three bends required to get through the dipstick opening, the case halves, then around the crankshaft, to reach the camshaft.

Even if it were, by the time you got to the cam, the lens would be smeared with oil.

I don't know, if doctors can snake a tiny tube through a leg, up an artery, and inspect the heart, then surely we can push a big camera around a few bends of metal.

[Pinecone]

16 hours ago, 201Steve said:

Be real cool if you could just have a gosh darn inspection hole somewhere on top of the case threaded in. 

That is what I was thinking.

Hmm, drill and tap a hole to inspect and seal after.

[Pinecone]

59 minutes ago, MattCW said:

I don't know, if doctors can snake a tiny tube through a leg, up an artery, and inspect the heart, then surely we can push a big camera around a few bends of metal.

Except that is inserted in a tube that goes to the place you want to see.

[A64Pilot]

On 1/22/2025 at 9:30 AM, AJ88V said:

 Can the A&P performing the pre-buy inspection ground the airplane if they find (claim) a discrepancy?

I believe ONLY the FAA can ground an aircraft. Whatever grounding means, not to be cute but what does it mean, exactly?

As an IA I know I cannot, What I am supposed to do say if I perform an Annual and discover a Very unsafe condition is sign off the Annual and state I gave the owner a list of discrepancies. I’ve never had to do that. If I ever do I think I’ll try to get the owner to sign for the list to cover myself.

Basically I think I’d sign it off by saying an Annual insp has been completed and the aircraft found to be unairworthy, a list of discrepancies was provided to the owner.

Now I said it was found to be in an unairworthy condition, because it is, is that grounding it?

 

[A64Pilot]

2 hours ago, Pinecone said:

That is what I was thinking.

Hmm, drill and tap a hole to inspect and seal after.

I’m sure that would render the case unairworthy, but I know you were kidding.

If you we’re really serious an STC would be how it’s done, involving at least a powerplant DER

 

Edited January 23 by A64Pilot

[jetdriven]

I had a client took his plane to a shop at another airport in the DC area, and they handed him a discrepancy list of like $25,000 worth of stuff, but looking at the list it looked to be about 4000 bucks of stuff.  When he showed him, the documentation that a few of the write ups were trivial and actually allowed by the manufacturer, or how you could treat the corrosion on the rear wing attached fitting without pulling the wing off, the shop rolled his plane outside told him to go F himself and then faxed the discrepancy list to the Washington FSDO and told him the plane had  to leave on a trailer. I fixed the three discrepancies that were legitimate on the ramp and then we ferried it over to my shop and fixed the rest.  The FSDO guy said he’s not giving a ferry permit, even though I had inspected the aircraft, so we got the DER that he hired to engineer the wing skin crack repairs to state that it was safe for not more than 100 hours of flight time.  Then he called the FSDO and got into a fight with the inspector because he still refused to give a ferry permit saying it was unairworthy, even though the DER says you don’t get to tell me that it’s not airworthy because I’m actually a designated engineering representative of the FAA and I’m telling you that it is.  But it was really crazy how that went.

[201Steve]

9 hours ago, jetdriven said:

The engine shop cut your engine life in half.  But at least they saved 50$.  
but seriously I put this in writing and verify it before taking delivery. It’s that important.

It was in writing. I don’t think it was a money issue as much as they were not available at the time. This was the year 2021 where you couldn’t get anything. That’s not an excuse, as I pointed out ever so professionally. I told them it was not their right to substitute, it was mine; and the burden of availability should have been my issue which I promise I would’ve resolved. Anyway, what do you do? 2 overhauls in one year, very little flying happening, I have it back, how do you rectify that? I just figure if I have an issue and the shop is still owned by the same, I will be making a visit with a reminder. All I can do. In the meantime, I run a black max engine dehumidifier. 

[201Steve]

5 minutes ago, jetdriven said:

the shop rolled his plane outside told him to go F himself and then faxed the discrepancy list to the Washington FSDO and told him the plane had  to leave on a trailer.

When you give a d bag a badge, they think they are King Kong. That guy needs his ass kicked.