Is this cam hosed?

[Grandmas Flying Couch]

My engine had a history of dirt ingestion through the alternate air door.  When converting it away from turbo at last overhaul (2013) they installed a weak incorrect spring that opened with almost no pressure.  I ordered the factory spring and seal but I was too late and the damage was done.  I decided to do a top iran since the engine only has 400 hr smoh.  When I pulled the worst cylinder I saw this on the intake lobe shared by the front cylinders.  Take a look at the pics appears to be pitting.  The followers look perfect.  It almost seems to be metallurgical problem with chunks missing.  Is this cam hosed?  

Also look at this wrist pin bushing, is this abnormal wear?  I worry dirt contaminated the oil and ruined bottom end.  

May have to euthanize her at 400 hrs.  

Thanks Guys!

Notes: use 100 weight, change often, spin on filter, use cam guard, fly often, Live in phoenix.  Have engine monitor, did not send in oil samples.  

 

[carusoam]

That surely isn’t an ordinary smooth surface of a cam lobe…

The cratering will keep oil from being able to lubricate the surface….properly.

It is odd that the followers aren’t showing a reaction to running across this rough surface…

 

So…

Lets ask the doc… @M20Doc (cam lobe pic with craters…)

Best regards,

-a-

[WeldWade]

Every camshaft with beginning lobe failure that I've ever seen looked like that. If it were me I'd replace it. 

[N201MKTurbo]

That cam will probably run for hundreds of hours. You can replace it now, or wait and keep an eye on it. You can measure the valve lift at the valve without taking the engine apart. It will wear away slowly. 
 

There are quite a few planes flying with wear like that that nobody knows about, because they haven’t pulled a cylinder. It is your decision. It isn’t the kind of thing that will cause catastrophic engine failure, you will just slowly lose power in that cylinder. 

[Guest]

The camshaft is done, time for a new one with a set of DLC lifters.

Clarence

[N201MKTurbo]

7-31. Camshaft (Visual Inspection). Carefully inspect
all surfaces of the camshaft for cracks, scoring, galling,
corrosion, pitting or other damage; be particularly
careful when inspecting bearing surfaces. If a
hydraulic tappet body has been rejected for spalllng,
inspect the corresponding cam lobe. Any indication of
distress, surface irregularity or feathering at the edge
of the cam lobe is cause for rejection of the camshaft.

 

This is the inspection criteria for re-using a cam at overhaul. I can't find any criteria for taking a cam out of service. It certainly fails the inspection for re-use, but should you replace the cam now? I have seen cams and tappets that were way worse than that in engines that were working fine. Will it make it to overhaul? probably not. Will it run for a bunch of more hours? probably. It will cost $10,000 to repair it.

[1964-M20E]

The bigger question is how far do you want to take this.  You just OH the engine 400 hours ago so no real reason to do a "OH"  It appears that you are in a position of remove and replace engine and open the case.

1. Is your mechanic comfortable with opening the case and changing the cam?
2. How mechanically inclined are you and wiling to get you hands dirty during this process?
3. Inspect the main bearings for signs of wear
4. Rod bearings; you can disassemble the case without unbolting the rods (save on the $80 per rod bolts).  If main bearings look good don't touch the rods.
5. Oil pump gears 400 hours inspect and reuse
6. Inspect accessory case gears
7. clean crank case and prepare for reassembly with new cam and followers
8. New engine gasket kit
9. Leave the pistons in the cylinders during disassembly and reuse rings unless you really want to change them
10. Reassemble the engine and install on aircraft.
11. Once done you will have a 400 hour engine with a new cam and lifters.

JMHO

[David Lloyd]

Sometimes a cam can be reground.  That one is toast.  

[chriscalandro]

Who did the OH? It’s almost like that was there when it went in. 

[EricJ]

It's definitely revealed itself as something to keep an eye on, but I'll +1 that it's unlikely to cause any issues other than wearing down prematurely and causing gradual power loss.    If the engine makes static rpm then there's no compelling reason I'm aware of to change it.   I'd watch oil analysis and monitor the oil filter against the Lycoming recommendations (which allow metal in the filter), and see how much life you can get out of it.

 

[N201MKTurbo]

58 minutes ago, 1964-M20E said:

The bigger question is how far do you want to take this.  You just OH the engine 400 hours ago so no real reason to do a "OH"  It appears that you are in a position of remove and replace engine and open the case.

1. Is your mechanic comfortable with opening the case and changing the cam?
2. How mechanically inclined are you and wiling to get you hands dirty during this process?
3. Inspect the main bearings for signs of wear
4. Rod bearings; you can disassemble the case without unbolting the rods (save on the $80 per rod bolts).  If main bearings look good don't touch the rods.
5. Oil pump gears 400 hours inspect and reuse
6. Inspect accessory case gears
7. clean crank case and prepare for reassembly with new cam and followers
8. New engine gasket kit
9. Leave the pistons in the cylinders during disassembly and reuse rings unless you really want to change them
10. Reassemble the engine and install on aircraft.
11. Once done you will have a 400 hour engine with a new cam and lifters.

JMHO

Lycoming insists you don't reuse certain items when you crack the case. There is a service bulletin about it. What comes to mind are the main bearings and the piston pin caps. 

You can get the cam reground for about 1/3 the price of a new cam. The cam in question can probably be reground. The cam grinders will certify the cam, so it is up to them if they can do it or not. You will have to replace all the tappet bodies too. They can be reground also. The valve lash will need to be set up after it is assembled, this may require a push rod or two.

[1964-M20E]

14 minutes ago, N201MKTurbo said:

Lycoming insists you don't reuse certain items when you crack the case. There is a service bulletin about it. What comes to mind are the main bearings and the piston pin caps. 

You can get the cam reground for about 1/3 the price of a new cam. The cam in question can probably be reground. The cam grinders will certify the cam, so it is up to them if they can do it or not. You will have to replace all the tappet bodies too. They can be reground also. The valve lash will need to be set up after it is assembled, this may require a push rod or two.

You are citing SB240W.

1. I believe SBs are optional for part 91 operations not mandatory.
2. If you want to call it an overhaul you need to replace all the items listed.  I did this on my overhaul.
3. It says "AT OVERHAUL OR UPON REMOVAL:" and the SB lists 11  specific things some of which do not apply to the IO360 A1A engine.  Below are the items I believe apply to the A1A engine.
   • lock nuts and washers
   • bearings main and rod
   • camshaft gear bolts you getting a new cam and these are not very expensive anyway.
   • connecting rod bolts and nuts.  It could be argued if you do not unbolt the rods you do not  need to change these i.e,. not removed.  Unbolt the rods and yes you should change the bolts since they are stretch type bolts.
   • Crankshaft gear bolt, it could be argued that if you do not take the crankshaft gear off you do not need to replace this bolt i.e. not removed.
4. The next section states "AT OVERHAUL:"  If you are not calling this an overhaul then these do not apply at all.

However, anything internal to the case you probably should consider replacing.

Again JMHO I'm not a A&P mechanic but I have identified as one lately.

 

 

 

 

SB240W Mandatory Parts Replacement at Overhaul.pdf

[Grandmas Flying Couch]

12 hours ago, WeldWade said:

Every camshaft with beginning lobe failure that I've ever seen looked like that. If it were me I'd replace it. 

That's what I'm thinking.  

8 hours ago, N201MKTurbo said:

That cam will probably run for hundreds of hours. You can replace it now, or wait and keep an eye on it. You can measure the valve lift at the valve without taking the engine apart. It will wear away slowly. 
 

There are quite a few planes flying with wear like that that nobody knows about, because they haven’t pulled a cylinder. It is your decision. It isn’t the kind of thing that will cause catastrophic engine failure, you will just slowly lose power in that cylinder. 

I believe it would, but since all four cylinders have to come off and I know about the cam I will probably take the engine home and put a cam in it.  

7 hours ago, M20Doc said:

The camshaft is done, time for a new one with a set of DLC lifters.

Clarence

I'm going to see if I can get ahold of those diamond lifters.  Mine are still smooth at the least the front ones are.  

2 hours ago, 1964-M20E said:

The bigger question is how far do you want to take this.  You just OH the engine 400 hours ago so no real reason to do a "OH"  It appears that you are in a position of remove and replace engine and open the case.

1. Is your mechanic comfortable with opening the case and changing the cam?
2. How mechanically inclined are you and wiling to get you hands dirty during this process?
3. Inspect the main bearings for signs of wear
4. Rod bearings; you can disassemble the case without unbolting the rods (save on the $80 per rod bolts).  If main bearings look good don't touch the rods.
5. Oil pump gears 400 hours inspect and reuse
6. Inspect accessory case gears
7. clean crank case and prepare for reassembly with new cam and followers
8. New engine gasket kit
9. Leave the pistons in the cylinders during disassembly and reuse rings unless you really want to change them
10. Reassemble the engine and install on aircraft.
11. Once done you will have a 400 hour engine with a new cam and lifters.

JMHO

I do my own work, I've had too many problems, my mechanic inspects asks a ton of questions and then signs it off.  I would love to replace the cam I would have to ask him if he's cool with going this far.  With 400 hours of inadvertent dirt ingestion, I would love to replace all bearings inspect and measure all gears and journals etc.  Piston rings are toast, I pulled number 2 because of excessive oil in the barrel and the oil control ring fell out in 7 or 8 pieces as I pulled the jug.  

1 hour ago, EricJ said:

It's definitely revealed itself as something to keep an eye on, but I'll +1 that it's unlikely to cause any issues other than wearing down prematurely and causing gradual power loss.    If the engine makes static rpm then there's no compelling reason I'm aware of to change it.   I'd watch oil analysis and monitor the oil filter against the Lycoming recommendations (which allow metal in the filter), and see how much life you can get out of it.

 

Since the engine has to have a top Iran anyway will probably yank it and change the cam with a new one perhaps the superior cam is superior as this looks like a metallurgical failure the other visible lobes are perfect.  

58 minutes ago, N201MKTurbo said:

Lycoming insists you don't reuse certain items when you crack the case. There is a service bulletin about it. What comes to mind are the main bearings and the piston pin caps. 

You can get the cam reground for about 1/3 the price of a new cam. The cam in question can probably be reground. The cam grinders will certify the cam, so it is up to them if they can do it or not. You will have to replace all the tappet bodies too. They can be reground also. The valve lash will need to be set up after it is assembled, this may require a push rod or two.

I would get it reground to save cheese but the problem seems metallurgical perhaps a bad heat treat because the metal is flaking off in what looks like a brittle granular event.  Not due to corrosion or bad lifters, the lifters are smooth.  I have one extra pushrod but would likely have to order a couple.   

22 minutes ago, 1964-M20E said:

You are citing SB240W.

1. I believe SBs are optional for part 91 operations not mandatory.
2. If you want to call it an overhaul you need to replace all the items listed.  I did this on my overhaul.
3. It says "AT OVERHAUL OR UPON REMOVAL:" and the SB lists 11  specific things some of which do not apply to the IO360 A1A engine.  Below are the items I believe apply to the A1A engine.
   • lock nuts and washers
   • bearings main and rod
   • camshaft gear bolts you getting a new cam and these are not very expensive anyway.
   • connecting rod bolts and nuts.  It could be argued if you do not unbolt the rods you do not  need to change these i.e,. not removed.  Unbolt the rods and yes you should change the bolts since they are stretch type bolts.
   • Crankshaft gear bolt, it could be argued that if you do not take the crankshaft gear off you do not need to replace this bolt i.e. not removed.
4. The next section states "AT OVERHAUL:"  If you are not calling this an overhaul then these do not apply at all.

However, anything internal to the case you probably should consider replacing.

Again JMHO I'm not a A&P mechanic but I have identified as one lately.

 

 

 

 

SB240W Mandatory Parts Replacement at Overhaul.pdf 221.78 kB · 2 downloads

Washers, lock nuts, bearings, stretch bolts cylinder nuts, and a few other inexpensive wear items would be on my list for sure.  Alot of dirt in circulation.  

[1964-M20E]

Connecting rod bolts are about $80 each.  

I'm like you I like turning the wrenches myself.

Since you said the rings in #2 were toast I'd get all new rings and hone the cylinders. Not a huge expense and you are there already.  More of  PIA to go back later.

 

 

 

[Grandmas Flying Couch]

Just now, 1964-M20E said:

Connecting rod bolts are about $80 each.  

I'm like you I like turning the wrenches myself.

Since you said the rings in #2 were toast I'd get all new rings and hone the cylinders. Not a huge expense and you are there already.  More of  PIA to go back later.

 

 

 

That's the plan, #3 has was appears to be gouges, if the hone doesn't remove them, ill buy one new jug. 

[N201MKTurbo]

55 minutes ago, Grandmas Flying Couch said:

That's what I'm thinking.  

I believe it would, but since all four cylinders have to come off and I know about the cam I will probably take the engine home and put a cam in it.  

I'm going to see if I can get ahold of those diamond lifters.  Mine are still smooth at the least the front ones are.  

I do my own work, I've had too many problems, my mechanic inspects asks a ton of questions and then signs it off.  I would love to replace the cam I would have to ask him if he's cool with going this far.  With 400 hours of inadvertent dirt ingestion, I would love to replace all bearings inspect and measure all gears and journals etc.  Piston rings are toast, I pulled number 2 because of excessive oil in the barrel and the oil control ring fell out in 7 or 8 pieces as I pulled the jug.  

Since the engine has to have a top Iran anyway will probably yank it and change the cam with a new one perhaps the superior cam is superior as this looks like a metallurgical failure the other visible lobes are perfect.  

I would get it reground to save cheese but the problem seems metallurgical perhaps a bad heat treat because the metal is flaking off in what looks like a brittle granular event.  Not due to corrosion or bad lifters, the lifters are smooth.  I have one extra pushrod but would likely have to order a couple.   

Washers, lock nuts, bearings, stretch bolts cylinder nuts, and a few other inexpensive wear items would be on my list for sure.  Alot of dirt in circulation.  

I have an engine stand and an assembly stand. If you want to drive over to CHD you are welcome to use them. I can give you some helpful hints about assembly that will make your life easier.

[EricJ]

3 hours ago, Grandmas Flying Couch said:

Since the engine has to have a top Iran anyway will probably yank it and change the cam with a new one perhaps the superior cam is superior as this looks like a metallurgical failure the other visible lobes are perfect.  

You're across the valley from me, but holler if you need a hand with it.

 

[Guest]

Because the engine is low time since the last overhaul, you don’t have to re do the overhaul.  I’d do the best possible repair with good documentation of everything you do to add future value should you sell it.

Clarence 

[MBDiagMan]

Sure looks like you would find iron in the oil filter.  The lifter concerns me much more than the cam.  That is where I was with mine in January.  We split it and found other things wrong to a point of doing an overall.  I fully expect that I could have run mine a while longer, but it was a metal flake producing factory and I wasn’t comfortable letting that go through the oil pump before being tapped by the filter.

It’s only my opinion, but I’m very pleased that I got my hands on a set of the new Lycoming lifters with the DLC coating.  If I were you I would at the very least replace the cam and use a new set of Lycoming lifters.

 

[WeldWade]

Spring pressure problem, valve guide problem, lash problem possible. Too late to check lash but I would be checking spring pressure on every spring and the guides. Do you have a bent push rod? Don't rule out a valve train issue. I'm not an aircraft mechanic but I've worked on engines all my life. Looks like a possible loose lash situation to me. 

Poor heat treat or metallurgical issues usually aren't just one lobe in my experience. 

Just my .02 from my experience with racecar stuff.

[Grandmas Flying Couch]

6 hours ago, N201MKTurbo said:

I have an engine stand and an assembly stand. If you want to drive over to CHD you are welcome to use them. I can give you some helpful hints about assembly that will make your life easier.

I may take you up on that, that's awesome of you!  I'm still mulling the shock and going over my options.  

4 hours ago, EricJ said:

You're across the valley from me, but holler if you need a hand with it.

 

I will as soon as I figure out which way I'm going!

4 hours ago, M20Doc said:

Because the engine is low time since the last overhaul, you don’t have to re do the overhaul.  I’d do the best possible repair with good documentation of everything you do to add future value should you sell it.

Clarence 

I'm leaning in the direction of replacing everything that is relatively cheap like bearings that look less than new, the cam shaft, the lifters, things like that.  

2 hours ago, MBDiagMan said:

Sure looks like you would find iron in the oil filter.  The lifter concerns me much more than the cam.  That is where I was with mine in January.  We split it and found other things wrong to a point of doing an overall.  I fully expect that I could have run mine a while longer, but it was a metal flake producing factory and I wasn’t comfortable letting that go through the oil pump before being tapped by the filter.

It’s only my opinion, but I’m very pleased that I got my hands on a set of the new Lycoming lifters with the DLC coating.  If I were you I would at the very least replace the cam and use a new set of Lycoming lifters.

 

I hear you, I don't feel good about running it this way.  I will see if I can grab some DLC lifters.  

1 hour ago, WeldWade said:

Spring pressure problem, valve guide problem, lash problem possible. Too late to check lash but I would be checking spring pressure on every spring and the guides. Do you have a bent push rod? Don't rule out a valve train issue. I'm not an aircraft mechanic but I've worked on engines all my life. Looks like a possible loose lash situation to me. 

Poor heat treat or metallurgical issues usually aren't just one lobe in my experience. 

Just my .02 from my experience with racecar stuff.

That is a good point, I hadn't thought of.  The other lobes look good.  

[MBDiagMan]

Yeah, I grew up in my Dads car shop and have seen some things myself.  In this case, however, this is exactly what my Lycoming cam and lifters looked like after a long storage period, and it was a result of corrosion.  The line of corrosion across the lobe was almost certainly a result of it setting still for some extended period of time, and almost certainly it set against the lifter who’s face is seen in the picture.  I can not see the adjacent lifter, but I would be willing to wager that it is worn but not spalled.  The corrosion causes a pit that starts tearing out one small piece at a time much like a pot hole.  Those small pieces look like a Christmas Tree ornament when seen in the cut open filter.

The currently produced Lycoming DLC coated lifters are said to virtually eliminate this problem.  I believe it.

[hammdo]

I keep hearing about the DLC 'cam followers' taking care of the sprawling issue but, I still see some original followers in great shape - yet the cam is shot. How will DLC followers solve what might be a metallurgy issue with the cam?

I guess time in service will tell...

Just playing devil's advocate....

-Don

 

[MBDiagMan]

The DLC will go a long way toward solving the corrosion problem, but it’s not a panacea.

The time in service thus far has proved quite encouraging.

[carusoam]

Cams and cam followers have two different challenges…

And sometimes the bad cam follower cuts down the cam lobe….  Making the cam lobe look like the bad guy…

Cam lobes are surface hardened and doesn’t take much time for a cutting tool follower to get through…

Of course, anything that disrupts the surface of the lobe (like rust) allows the removal of the hardened surface…

 

For lubrication to occur… we need two flat plates that approach each other at a bit of an angle…. The flatter the surfaces the less oil is required to lubricate them…

When oil is allowed to escape into holes, cracks, or out the sides of the contact areas…this allows the metal to metal contact that is so hazardous…

So… DLC coating on the follower will keep it from turning into a cutting tool…. If it works as designed…

Whatever it takes to maintain two smooth, hard surfaces… will be  dry helpful…

 

Do roller bearings have DLC coating?

The wheel + oil seems to be a nice combination to keep two metal surfaces from contacting each other in a sliding fashion…

PP thoughts only, not a metallurgist… MS does have a metallurgist… around here somewhere…

Best regards,

-a-