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Lycoming cam inspection

pa38112

Well Known Member
There has been much discussion about corrosion on Lycoming cams and the risk of buying a sitting engine. I have to believe there is a way to get a borescope somewhere to view the cam with-out splitting the case. I could not find a cut-away drawing with a quick search. Wouldn't one be able to fish a borescope up through the oil drain plug to view the cam lobes?
 
Don't think so...

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The easiest way is to pull a cylinder back for access.
Ryan

If this is done, I've heard that you don't want to remove the cylinder completely from the piston. What kind of cylinder base gaskets do Lycomings have? Wouldn't that have to be replaced any time you unbolt a cylinder? Seems like you would have to pull the cylinder all the way out to get a gasket installed?

I ask this because I'm in the market for an RV and some have sat for extended periods and I would want a mechanic to pull 2 cylinders and verify no cam corrosion.
Josh
 
If this is done, I've heard that you don't want to remove the cylinder completely from the piston. What kind of cylinder base gaskets do Lycomings have? Wouldn't that have to be replaced any time you unbolt a cylinder? Seems like you would have to pull the cylinder all the way out to get a gasket installed?
I ask this because I'm in the market for an RV and some have sat for extended periods and I would want a mechanic to pull 2 cylinders and verify no cam corrosion.
Josh

Cylinder base uses an "O" ring. The trick is to carefully pull the cylinder just past the wrist pin. Remove the wrist pin leaving the piston/rings in the cylinder.
This is not quite as easy as it sounds. The bottom ring is very close to the wrist pin. Goos Luck!
 
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I ask this because I'm in the market for an RV and some have sat for extended periods and I would want a mechanic to pull 2 cylinders and verify no cam corrosion.

This is why I posed the original question. Not many owners are going to let you pull 2 cylinders, and you are risking a maintenance induced failure. If there is any way to inspect with a borescope, that would be the best.
The photo snopercod posted helps explain why this is difficult - thank you for sharing! - What about through the mag port?
 
This is why I posed the original question. Not many owners are going to let you pull 2 cylinders, and you are risking a maintenance induced failure. If there is any way to inspect with a borescope, that would be the best.
The photo snopercod posted helps explain why this is difficult - thank you for sharing! - What about through the mag port?

Nope - the Mag port won't get you to the cam lobes either. the only real way in to teh cam is to pull jugs. That's either a no-brained or a horrifying thought, depending on your experience.

If you have enough experience to do it, then its a no brainer. If the thought is horrifying....then you probably don't have the experience, and should hire someone who does.

Paul
 
- What about through the mag port?

Nope. The only way to inspect is pull a front and rear cylinder. Really it is the cam followers that need close inspection, they typically fail first. Even if you somehow managed to get a camera-on-a-stick in there, you need the valve train above the follower relaxed to get clearance enough to run a finger over the parts, wipe off the oil, and see things clearly.
Other than pull two cylinders, your best indicator would be a good oil filter inspection, and a look at how it?s been stored and flown.
Tim Andres
 
How big is the gap underneath the sump? the head of my articulating borescope is only about 1/4"

Caleb
 
Even if it was possible to thread it up through the sump, how would you do that without getting oil on the camera lens? You are bound to hit something covered in oil somewhere.

E
 
If this is done, I've heard that you don't want to remove the cylinder completely from the piston. What kind of cylinder base gaskets do Lycomings have? Wouldn't that have to be replaced any time you unbolt a cylinder? Seems like you would have to pull the cylinder all the way out to get a gasket installed?

I ask this because I'm in the market for an RV and some have sat for extended periods and I would want a mechanic to pull 2 cylinders and verify no cam corrosion.
Josh

I am sure I will catch some flack for this but here goes.
It is possible to pull back the cylinder without breaking the seal between the rings and the cylinder. It is a two person job. Prior to pulling the jug back make sure that cyl is on TDC on the compression stroke. Pull the cylinder only as far back as the wrist pin. One person will support the jug while the other inspects. When the inspection is complete remove the two lifters with a magnet and bleed them down then reinstall. The cylinder base gasket is an Oring that will stretch like a rubber band. Cut off the old one and stretch the new one around the cylinder and install. Replace the two rubber seals for the pushrod tubes reinstall the cylinder and torque.
This is my .02 cents take it for what its worth.
I have tried inspecting from the lower case area it is very difficult if not impossible to see everything your looking for.
Ryan
 
Before going through the exercise of pulling cylinders, you may want to consider how necessary that may be. If the plane has been sitting for several years in a wet climate, such as your home state, and the engine wasn't pickled, or at least a fresh oil change made before it was parked, you should be more concerned than if it's sitting in Az, Co, or NM and was put away with some care. Just something to keep in mind before spending the $ to pull jugs.
 
"...breaking the seal between the rings and the cylinder." I've heard this kind of thing a number of times and don't really understand it. I even had an A&P proclaim something like if you separate the piston from the cylinder at all, you have to re-ring, gap, hone the cylinder! Where does this silly talk come from? It seems a bit pervasive that some think there is a magic genie in that bottle that can't be put back. Of course, I assume that if you're prepared to have a cylinder in your hand, that you also have a ring compressor and know how to use it...
 
Single data point

Before going through the exercise of pulling cylinders, you may want to consider how necessary that may be. If the plane has been sitting for several years in a wet climate, such as your home state, and the engine wasn't pickled, or at least a fresh oil change made before it was parked, you should be more concerned than if it's sitting in Az, Co, or NM and was put away with some care. Just something to keep in mind before spending the $ to pull jugs.

We bought an RV-7A project that had a two hour old Titan/ECI Lycoming O-360 clone. Engine had been pickled after assembly/test run and was in Grand Junction, CO in a heated workshop for about 5 years. Most of the advice I received was "it will be fine" but my gut told me differently.

We pulled the engine, sent it to Penn Yan and they found a corroded cam and lifters. The two lifters with corrosion were sitting on the tip of the cam lobe. Again, this is just a single data point and I can't tell you with any degree of certainty that the engine was in a controlled environment the whole time. However, I'm really glad we sent the engine to Penn Yan.
 
We bought an RV-7A project that had a two hour old Titan/ECI Lycoming O-360 clone. Engine had been pickled after assembly/test run and was in Grand Junction, CO in a heated workshop for about 5 years. Most of the advice I received was "it will be fine" but my gut told me differently.

We pulled the engine, sent it to Penn Yan and they found a corroded cam and lifters. The two lifters with corrosion were sitting on the tip of the cam lobe. Again, this is just a single data point and I can't tell you with any degree of certainty that the engine was in a controlled environment the whole time. However, I'm really glad we sent the engine to Penn Yan.

And on the other hand, the IO-360 in my -6 was a 2000-hr runout "core" which had been stored in the crawl space under a house in the San Francisco area for at least 5 years before I bought it. I removed 2 cylinders to inspect the cam/followers and they were perfect (well, no corrosion). Also removed the gear train housing and the oil pan for inspection, and then flew it as-is for 100 hours before overhauling it.

Heinrich
 
And on the other hand, the IO-360 in my -6 was a 2000-hr runout "core" which had been stored in the crawl space under a house in the San Francisco area for at least 5 years before I bought it. I removed 2 cylinders to inspect the cam/followers and they were perfect (well, no corrosion). Also removed the gear train housing and the oil pan for inspection, and then flew it as-is for 100 hours before overhauling it.

Heinrich

To the point of the original post, I believe the only practical way to properly inspect the cam is to open up the engine. Pulling and reinstalling individual cylinders and the potential for issues has certainly been discussed by Mike Busch and others. But I know that is done daily, most of the time without creating additional problems. It wasn't the right choice for me.

In our case, removing the engine from the RV-7 project took me 45 minutes (and I've never removed an airplane engine before). It was a practical decision since engine removal from a flying airplane would have been much more difficult . Ultimately repairing an engine that was making metal would likely have been much more costly.

I'm not sure I understand the reluctance to spend a few dollars up front- if for no other reason than peace of mind. We spend tens of thousands (in many cases much more) on these flying machines, yet we worry about a few more dollars ensuring that the single means of propulsion is in good shape.
 
I'm not sure I understand the reluctance to spend a few dollars up front...
I think the reluctance is more related to what you're liable to find. If your inspection discovers a spalled tappet or cam, you're looking at a $10,000 repair, not just a few dollars. It's like that old saw, "Don't ask the question if you're not willing to accept the answer."
 
I think the reluctance is more related to what you're liable to find. If your inspection discovers a spalled tappet or cam, you're looking at a $10,000 repair, not just a few dollars. It's like that old saw, "Don't ask the question if you're not willing to accept the answer."

I disagree with your numbers only on the basis of my limited experience. Penn-Yan found a corroded cam and lifters plus they found some damage to one of the cylinders and pistons presumably from the original engine test run. Penn-Yan replaced the cam and lifters, all four pistons and rings (installed 9.5 to 1), honed the cylinders, converted from O-360 to IO-360 (my parts), painted the engine, of course inspected everything and ran in their test cell. Including shipping to and from Oregon, I paid less than $10,000. If you have to hire someone to do the removal and reinstall, and it's on a flying airplane, then I guess your number might be correct.

I still don't agree with not inspecting the engine when you suspect there is corrosion. I guess my tolerance for risk is much lower than some...
 
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"...breaking the seal between the rings and the cylinder." I've heard this kind of thing a number of times and don't really understand it. I even had an A&P proclaim something like if you separate the piston from the cylinder at all, you have to re-ring, gap, hone the cylinder! Where does this silly talk come from? It seems a bit pervasive that some think there is a magic genie in that bottle that can't be put back. Of course, I assume that if you're prepared to have a cylinder in your hand, that you also have a ring compressor and know how to use it...

You are correct. This comes from the old days when we had to ridge ream a cylinder before removing a piston on a well worn engine. If we did not we risked damaging a ring by catching it on the ridge while trying to pull the piston out of the hole. If you go slow and easy and protect the rings you can get by with removing the piston. But Mel is right on an engine with jugs it is safer and faster to leave the piston in the jug and slide the wrist pin out. There is a catch to that however. Some of the newer aircraft pistons do use a wrist pin with a retainer clip holing them in and not the old wrist pin wear cap style installation. The main goal is to protect the rings as they are many times damaged easily. There are ring compressors that are used to put the jug back over the piston with the rings and then take the tool off around the connecting rod. But what it all boils down to is how comfortable the Tech. is at doing that job. Some times on a jug removal you miss that oil ring by a little and it pops out. Your not going to change the rings and ball hone over that. You just be very careful and gently compress that ring back into place.
Just the way it has been in the field for longer than me for sure.
Yours, R.E.A. III # 80888
 
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There has been much discussion about corrosion on Lycoming cams and the risk of buying a sitting engine. I have to believe there is a way to get a borescope somewhere to view the cam with-out splitting the case. I could not find a cut-away drawing with a quick search. Wouldn't one be able to fish a borescope up through the oil drain plug to view the cam lobes?
An articulated fiberscope could be used to get up to the camshaft from the opening in the crankcase above the sump. As for what's visible with oil film on the lobes and follower, etc, that might introduce some uncertainty into your results. With a little patience and creativity, I've snaked fiberscopes deep into machinery. But for the cost to rent a quality tool and time, I would simply pull a cylinder. You should be able to see three cam lobes from any cylinder. Odds of three lobes being in good shape and the other three not are minuscule.
 
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"...breaking the seal between the rings and the cylinder." I've heard this kind of thing a number of times and don't really understand it. I even had an A&P proclaim something like if you separate the piston from the cylinder at all, you have to re-ring, gap, hone the cylinder! Where does this silly talk come from? It seems a bit pervasive that some think there is a magic genie in that bottle that can't be put back. Of course, I assume that if you're prepared to have a cylinder in your hand, that you also have a ring compressor and know how to use it...

Thread drift a bit here, but here goes anyway. I agree there is no magic genie escaping here. The only real danger to letting the rings escape the cylinder is the possibility of breaking the rings while trying to reinstall them into carbon fouled ring lands. Carbon in the ring lands can also interfere with the rings proper operation after reassembly once disturbed. It?s probably not that likely, but certainly is a possibility and it?s better not to pull them out. It?s also going to help keep dirt out of the assembly.
Tim Andres
 
Thread drift a bit here, but here goes anyway. I agree there is no magic genie escaping here. The only real danger to letting the rings escape the cylinder is the possibility of breaking the rings while trying to reinstall them into carbon fouled ring lands. Carbon in the ring lands can also interfere with the rings proper operation after reassembly once disturbed. It’s probably not that likely, but certainly is a possibility and it’s better not to pull them out. It’s also going to help keep dirt out of the assembly.
Tim Andres

Yes this is a concern. However it has been done for many years that if you have an engine that is torn down to inspect or needs a jug taken off for some reason. There are tools to clean the ring groves out, before you put the assembly back together. The ring grove cutters are not cheep from Snap-On or other suppliers but there is an old trick if you are going to re-ring and glaze break before you reassemble. Take the old rings and break or cut them with a grinder, then sharpen a taper at one end so you can use that as a tool to scrape the old carbon out of the ring grove. I have always thought it a good idea to clean the piston and it's ring groves before reassembly even if I was using the old rings and going right back together after inspection of the parts. Yes it is best to be very careful and keep all the parts in the same
relative place and orientation to one another. Think came-followers, lifters, push-rods, rocker-arm and so on. And yes there are special pliers to help take the rings off by gently expanding them at the ring gap.
Hope this helps. Yours, R.E.A. III # 80888

OH and "P.S." here you can go to Vlad about this one as I have seen pictures of his jug replacement of late. He knows the ropes on this one.
 
Its just crazy they still don't have a boss at the top of the crankcase to be used for inspection scopes. Its clear that Lycoming, Lyclones and Continental don't want you to know what is going on in there.
 
(I)O-540

Can the O-540 series Lycomings get a colonoscopy examination of one or two cam lobes through the oil filler tube location on top of the crankcase?
 
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