Spalled Camshaft

My Cub’s O-360 engine is in the overhaul shop. Today, they told me that the camshaft is unserviceable, rejected. Cam lobes for cylinders #1 & #2 are spalled. Recently, immediately prior to the engine going in for overhaul, #4 exhaust had a bent push rod and #3 had a stuck intake valve, both at the same time. 450 hrs before the decision to overhaul, all four cylinders got reworked, because exhaust valves on #2, #3 & #4 were stuck, but no bent push rods.

The previous engine overhaul was done by LyCon and a brand new camshaft was installed. They also reshaped the cam lobes to give the engine extra pep.

I’ve religiously changed the oil (Phillips 20w-50 x/c) & filter at 50 hrs (or less) throughout the engine’s 2250 hrs SMOH, along with 8oz of Camguard at every oil change (except during break-ins). The camshaft has the CentriLube STC that spritzes the camshaft with oil during operation.

My questions are these - is it normal for camshafts to spall when the engine reaches its overhaul time, especially a camshaft that started out brand new? Could all the valve sticking have caused the damage to the camshaft? Isn’t the extra oiling from the CentriLube and Camguard supposed to prevent this kind of damage to the camshaft? Could the coating that was put on the camshaft after the cam lobes were reshaped have been the failure that caused the spalling?

I’m just wondering what I could have done differently to have a better outcome. Although I did wear out the engine fair & square.
Thank you for your thoughts and advice.

windy

My guess... the reshaping.


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I had to replace my cam at about 1,300 hours. The plane did sit for 18 months without being flown, but it had a teardown 1 year after that for a prop strike and the cam looked great. Lycomings just seem to have some issues with the cams, some do some don't. I used the same oil/Camguard treatment and changed every 25 hours. I think reducing the amount of Lead in your fuel helps with the stuck valve issue, along with MMO in the fuel occasionally. While I was waiting for my SI to get done I was providing the plane with full tanks to some friends just to keep it flying.
DENNY

Why so many stuck valves? Don’t usually see that much on -360’s- even running straight avgas for 2000 hrs... I’d also have to suspect the reshaping/recoating/hardening process- not that these engines can’t benefit from a different cam profile, but it just seems you’re gambling any time you do anything to a cam after its left the manufacturer...

windy said:

My Cub’s O-360 engine is in the overhaul shop. Today, they told me that the camshaft is unserviceable, rejected. Cam lobes for cylinders #1 & #2 are spalled. Recently, immediately prior to the engine going in for overhaul, #4 exhaust had a bent push rod and #3 had a stuck intake valve, both at the same time. 450 hrs before the decision to overhaul, all four cylinders got reworked, because exhaust valves on #2, #3 & #4 were stuck, but no bent push rods.

The previous engine overhaul was done by LyCon and a brand new camshaft was installed. They also reshaped the cam lobes to give the engine extra pep.

I’ve religiously changed the oil (Phillips 20w-50 x/c) & filter at 50 hrs (or less) throughout the engine’s 2250 hrs SMOH, along with 8oz of Camguard at every oil change (except during break-ins). The camshaft has the CentriLube STC that spritzes the camshaft with oil during operation.

My questions are these - is it normal for camshafts to spall when the engine reaches its overhaul time, especially a camshaft that started out brand new? Could all the valve sticking have caused the damage to the camshaft? Isn’t the extra oiling from the CentriLube and Camguard supposed to prevent this kind of damage to the camshaft? Could the coating that was put on the camshaft after the cam lobes were reshaped have been the failure that caused the spalling?

I’m just wondering what I could have done differently to have a better outcome. Although I did wear out the engine fair & square.
Thank you for your thoughts and advice.

windy

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What was the calendar time interval between your oil changes? This is just as important as tach hours.

Windy, which year was your last overhaul and did you had some metallic particles in your oil filter after examination?
There was a Lycoming SI No.1543, dated February 23 2012 out there relating a batch of faulty tappets.

And look out for „Airworthiness Bulletin AWB 85-014“ from the Australian Civil Aviation Safety Authority !

... Investigations by various Lycoming engine overhaulers have found that in the majority of cases the filter contamination was directly attributed to severe spalling of the now superseded Lycoming tappet body P/N 15B26064. These tappet bodies were supplied from late 2009 until mid 2012 ...

I had severe spalling of my camshaft two years after major overhaul in 2011 (Lycoming O320) because of these tappets.

G44 said:

What was the calendar time interval between your oil changes? This is just as important as tach hours.

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I think Windy’s oil change interval is usually about two weeks or 50 hrs I’m also wondering if flying across N America 27 times could have attributed to some of the wear? That stinks either way!

Wendy's engine certainly sat less than many of us combined - although it could have been that two week break when she went to Antarctica. :lol:

sj

I would contact LyCon and see if your cam had the DLC coating. I am told since Lycoming started doing it they have ended their spalling issues. Up until the DLC coating it has been a crap shoot from my experience on cams spalling. I inspected my cam when I topped my engine back in the fall, luckily I have the roller cam that is not to prone to spalling.

Do you have an engine monitor Wendy?

LyCon had overhauled the engine in late 2011, so I’ll have to do some research to see if the offending tappets had been installed in my engine. I’ll also call LyCon to see what I can find out about what coating they used. 450 hrs ago, when the cylinders were out on vacation, the camshaft looked ok, from what could be seen. Those are good leads to follow up on. Thanks!

In the summer months, I’d usually change the oil & filter about every month and maybe go as long as three months between oil changes in the winter (like when I went to Antarctica, not in the Cub).

On the most recent oil change, there were a few, and I mean a VERY few, flecks of silver metal, non metallic. This was the first time I’d seen anything other than a few carbon globs.

I have an 8-point EI monitor, with all four CHTs and EGTs monitored. The EGTs run in the 1200-1350 range & the CHTs run in the 350-375 range in the summer (30-40 degrees cooler in the winter). The first batch of stuck valves occurred in summer & the second batch happened in winter.

The stuck valves had me perplexed. I’d have thought that getting the valve guides & exhaust valves replaced 450 hrs ago would have solved that problem. I used MMO intermittently during the last 450 hrs. Over the engine’s service life, I’ve used 100LL almost exclusively, except the times I was in Baja and had to use a tank of ethanol-free mogas to make it to the next Avgas stop. At least having multiple simultaneous stuck valves has made the decision making process a bit simpler.

I’m not complaining about the work that LyCon did on my previous engine overhaul. It was a strong, reliable engine for 8 years, until the very end. I’d have wished I could have flown it more hours before having to get it overhauled, but I did indeed get my money’s worth out of it and a priceless amount of fun.

For the current engine overhaul that is underway, I think I will definitely decline any option to reshape the cam shaft lobes. Another question: other than cost, is there any advantage one way or another for the replacement camshaft to be brand new or certified reconditioned?

Thank you all for the feedback

windy


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Reason I asked about the engine monitor was if you saw any indication before or during the stuck valves. Curious if it was running rich, cooler etc.

I would go new cam kit no question. Seen to many spalded cams and on a reconditioned there is no way to no how deep that hardened layer is. Tony changed his just after OSH this year for the exact same thing and he flies almost as much as you. Ken tells me he has seen no more spalded cams since Lycoming went to the DLC coating.

New cams for me, from now on

On the first batch of stuck valves, the EGT (and CHT to a lesser extent) told me exactly which cylinders had the stuck valves. On the second batch, it was a bit more subtle. The #4 EGT was running a bit cooler than it should have, which made me suspicious, but not sure. That’s the one that had the bent push rod, so maybe it was making a little bit of power. The #3 intake valve was stuck part way open on this last round, but the EGT looked completely normal, although the CHT was a bit lower than normal, but not enough to make me suspicious. And I get suspicious pretty easily.

P.S. I ALWAYS lean after I get leveled off after takeoff. Even when flying at sea level. Even though I have the engine monitor, I lean the old fashioned way - lean to peak RPM, then enrich a half turn. My plugs are always gray when I take them out to clean them.

Some of us that have had valve sticking wondered "why me". Years ago the various service letters and bulletins either hadn't been developed or were not commonly available before today's online access, especially for we owners. Here's a quick summary: https://www.tennesseeaircraft.net/2007/12/15/422/. Others are available from Lycoming.

Note that in addition to combustion byproducts and lead, intake air dirt combined with available lube can eventually collect in valve guides. That plus offset valve stem to guide wear leads to sticking as clearances are lost.

If at 50 hr oil changes even with filters you see the oil's built up more than the usual lead and carbon from increased blowby consider reducing the time between oil changes. Oils cheaper than fixing things in the long term.

Used oil analysis (UOA) can benefit if it's done over the life of the engine. Here's an example. Click on the Sample Reports for an example of implied guide wear:https://www.blackstone-labs.com/engine-types/aircraft/ If intake dirt bypasses the filter element or carb heat flapper silicon can increase.

Gary

When i overhauled Josh at Colorado airparts suggested the DLC ( diamond like carbon) cam and tappets
He said they were tearing down tbo engines and the cam/lifters were still like new
His number is 970-275-2900 if you would like to visit with him




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When valves start sticking rocker arm, cam, and lifter body face pressures rise. It would be nice if there were a facing that would outlast a bent pushrod event.

Gary

one other thought...

if valve is sticking open some... then the lifter is NOT riding up the cam as normal, and the cam is striking the HARD LIFTER with the HARD CAM... maybe chipping/knocking parts of face off, like in cold starts......... ?????

Stuck valves probably caused all of the problems. Just like a Hammer on the cam and lifters.

https://www.lycoming.com/content/operational-and-maintenance-procedures-avoid-sticking-valves

Advice like this and periodic oil analysis can help give a picture of the combustion process and deposits in the oil. Eventually deposits can cook off and form. The cylinders should be inspected at the recommended intervals suggested by the manufacturer (see #14). TBO isn't free.

Gary

According to that lycoming document, baffling can also contribute to stuck valves. See Gary, I still read! Lol

Tim it's baffling that anybody today reads and actually believes what they see. Nothing's 100% I admit, but when valve sticking happens it's quite real. I had it twice and the second cost me an overhaul that might have been prevented or delayed if we knew then what's available now.

First sign of spalling was silver sheen in the drain oil. Nothing at that time in the screen.

Gary

astjp2 said:

Stuck valves probably caused all of the problems. Just like a Hammer on the cam and lifters.

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Not unless the hydraulic lifters exceeded their travel.

Hydraulic lifters....not sure about aircraft but on Harleys it can take up to 10 minutes for a lifter to bleed down under pushrod and spring pressure when doing cam changes. When running I suspect an instantaneous valve sticking event may not allow for that bleed down and the cam/lifters get at the very least high surface pressures if not hammered over a portion of their travel. Would depend on where the valve stuck in its travel as well. Hence the bent pushrods that can happen when two inches of metal try to fit into one inch of space.

Gary

I'm fairly certain they are also making carbide lifters. I forget the company that has the STC.

Tim

The spalling is on cylinder #1 intake & exhaust lobes and one of the cylinder #2 lobes (the exhaust, I think). Interestingly, cylinder #1 was the only cylinder that never had any sticking valves.


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The hardened lifters I used in a 360 were from LyCon. I think they called them diamond coated, they are said to keep the cam clean and resistant to spalling. Not sure but I think they are made by Lycoming.

This is worth a read on valves, guides, and CHT temps: https://www.supercub.org/forum/showthread.php?43627-Valve-Guides-and-Lycoming-Engines

Gary

Adding a preoiler pump to the lube system can bring up pressure before starts. I had one on a PA-12-180 and there was no delay in indicated system pressure on startup.

Edit: It also had the drilled cam STC mod to let some oil out on the lobes.

And: Straight weight oils can stick around longer while sitting. I did a test on a bare piece of steel outdoors one summer. Shell 15-50, Shell 50W, and 20-50XC. The 50W was the last to leave the surface exposed to sun and rain.

Gary

BC12D-4-85 said:

Adding a preoiler pump to the lube system can bring up pressure before starts. I had one on a PA-12-180 and there was no delay in indicated system pressure on startup.

Edit: It also had the drilled cam STC mod to let some oil out on the lobes.

And: Straight weight oils can stick around longer while sitting. I did a test on a bare piece of steel outdoors one summer. Shell 15-50, Shell 50W, and 20-50XC. The 50W was the last to leave the surface exposed to sun and rain.

Gary

Click to expand...

Which oil was the first? My guess would be the 15-50. Right? Wrong?

Kurt