Me off all people...Cam and lifter failure

[N201MKTurbo]

I was working on a Jet Provost a few weeks ago. Its engine has a couple of pre oiler ports. If the engine hasn't been run in two weeks, you have to open the ports and give it a few squirts with an oil can before you start it.  They may have something there.

[KSMooniac]

I just remembered two more items/features on my wish list for Lycomings... it would be nice if the lifters were removable WITHOUT splitting the case (like Continental) and it would be handy if there were an inspection port somewhere in the case that could be used with a borescope to inspect the cam and lifters.  It would be as simple as a hole with a doubler/fitting and a threaded plug that could be removed for borescope access (like a jet engine case).

 

Sadly the regulatory and litigious climate will prevent any real improvements in the older products...

[jetdriven]

regulatory and litigious climate? Or corporate laziness?  Lycoming and Continental are building 50 year-old designs with little product improvement. In fact, the engines they build today are probably not as good as the units built 20-30 years ago. Look at the epidemic of Continental cylinder failures at 800 hours, or Lycoming camshaft/lifter problems. Almost every single one fails.  Seems Continental can't machine valves and seats concentric to the guide, and Lycoming can't make 1200 hours on a set of lifters.  Lycoming could have put roller tappets in their engines 30 years ago. My 1987 Mustang 5.0 had them, as did 1930s radial engines. All they had to do was re-engineer the engine to accept them, and get them approved. They certainly did, in 2005, and I bet it wasn't a big deal.

 

They only made the switch when their relentless outsourcing of parts bit them on the ass due to poor quality of metal, heat treating, and machining.  The parts put in factory engines fail with surprising regularity even compared to a couple decades ago. I dont think they give a shit about the quality of engines once they are past their warranty date. As John Deakin said, the factory rep's job is to snow you until you go away or the warranty expires.

 

They told me that 250 PPM of iron in the oil and iron fines in the filter is normal. Disregard oil analysis, even though thwir own documentation says that anything over 100 PPM/50hr is elevated. 

[aaronk25]

Aaron, was your aircraft parked outside or inside during the winter? The climate you have is similar to here I presume. I am wondering if your winter startup procedure might have anything to do with this?

Yves

Hanged all the time, even when traveling. All 6 oil analysis over the last 6 years have shown zero moisture in the oil. Most of my flights are 3-5 hours long as I fly a lot from my home base in MN to Atlanta or Jersey, non stop.

Not sure if a valve was sticking, but if it was there was no signs. Also on start up I get the engine up to 1050-1100rpms as fast as possible to get oil up on the cam. Always preheat and never, I mean never start the engine unless the oil is above 50 degrees. I even go as far as to bring my honda 2000 with me if preheat power is questionable, at small fields.

I'd love to know if there was something I could have done, but I'm guessing we're gonna caulk this up to faulty parts.

It's like anything in life, roll the dice!

[Alan Fox]

A roller lifter will not spall , It is a superior design , it is the difference between a friction bearing and a non friction bearing , In automotive we used to have cam lobe failures , in 30 years of working on cars , I have NEVER seen a roller lifter destroy a cam , I have seen MANY conventional lifters destroy cams on cars.......It is ABSOLUTELY a fix for the Lycoming cam problem......

[DaV8or]

The roller tappets don't do anything to address the lack of cam lubrication... the cam still sits up high, out of the oil, and without a direct oil path so it still has the same potential to corrode if left sitting for some period of time.

 

True, but if the cam corrodes, there is just a tiny contact patch where the ball rolls over the rust instead of a wider surface grinding over it. The roller engines have been out a little while now, has there been any cam/lifter failures? I really don't know the answer.

[jetdriven]

a couple roller camshafts I know of have had corrosion on the cam. But the problem was undetected until the engine was torn down due to a prop strike and it as discovered. it forms worm trails or rust spots on the cam but it appears to continue to operate without spalling or failure.

http://docthrock.com/TearDown.shtml

I emailed him and he replied, it sat un-pickled in his basement for a over a year, but still.

[cujet]

Another interesting point. I noticed that my Centrilube camshaft retained oil inside the bore after "pre oiling" during assembly. When rotated, the oil dripped and oozed out of the holes. I'm fairly certain that after a week of sitting, simple rotation of the engine spreads that oil on to the cam's exterior surface. 

 

I'd also guess that at least some of the cam lobes get instant oiling upon startup due to this.

[carusoam]

Is there a reason that the cam doesn't get a change to the raw material?

Plastics processing world uses some hard stainless steal and relies on less than perfect lubricants to keep running...

The raw material is 2X and the machining is more difficult, but the digital machining centers have removed the excess manpower that makes things ultra expensive.

If you can't add roller tappets...

Go ahead and drill for lubrication but use an improved alloy with that...

Best regards,

-a-

[pinerunner]

Hanged all the time, even when traveling. All 6 oil analysis over the last 6 years have shown zero moisture in the oil. Most of my flights are 3-5 hours long as I fly a lot from my home base in MN to Atlanta or Jersey, non stop.

Not sure if a valve was sticking, but if it was there was no signs. Also on start up I get the engine up to 1050-1100rpms as fast as possible to get oil up on the cam. Always preheat and never, I mean never start the engine unless the oil is above 50 degrees. I even go as far as to bring my honda 2000 with me if preheat power is questionable, at small fields.

I'd love to know if there was something I could have done, but I'm guessing we're gonna caulk this up to faulty parts.

It's like anything in life, roll the dice!

What about leaning? Did you lean for taxi? Etc. One fellow whose article I read and emailed did a bunch of analysis of problem valves with deposits on the stems. The deposits all had plenty of lead and something else that bound it together. The logical first choice for the something else would be the break-down products of incomplete combustion. His data led me to pay a lot of attention to leaning issues at low power. I know ROP vs LOP arguments get tiresome for some and apologize in advance. I am not an LOP troll.

[N601RX]

There has been some written about an increase rate of cam failures of flat tappet cams auto industry also.  Both Crane and Competition cams have published info about it.  The articles that suggest the increased rate of failures is due to changes in oil formulation over the last 20 years.

[carusoam]

Crane should have some experience with engines that sit... A lot.

Can you hear the tappets for about 15 seconds until the oil arrives?

Best regards,

-a-

[aaronk25]

What about leaning? Did you lean for taxi? Etc. One fellow whose article I read and emailed did a bunch of analysis of problem valves with deposits on the stems. The deposits all had plenty of lead and something else that bound it together. The logical first choice for the something else would be the break-down products of incomplete combustion. His data led me to pay a lot of attention to leaning issues at low power. I know ROP vs LOP arguments get tiresome for some and apologize in advance. I am not an LOP troll.

I lean immediately after start. A lot if times I find it's necessary to richen to get up taxi hills....so in short I lean brutally.

Until I was proved wrong by testwest, I did lop climbs if the plane was light.

[scottfromiowa]

So bottom line, does this engine have 1700 since overhaul? Aren't a lot of those hours before you bought the plane? As far as cause of failure...You will never know as the majority of the engines life was not supervised by the current owner. The newer engines with roller tappets don't have the experience/data points yet to know how "much better" they are. Time will tell.

When you inherit an engine there are a ton of unknowns. That it failed on the last quarter of a run to TBO while on the current owner/operators watch while doing "the right stuff" is of minor consequence. All this discussion is conjecture. Talk to the original owner and find out how he/she flew/maintained the plane...

Yes, I understand that there was a gear up and some repacements (engine parts) were made...Wasn't a major. Mix/mash. This is the result I would expect after 300-500 hours with a mystery higher time since major engine with field replacement of parts.

[mike_elliott]

The roller tappets don't do anything to address the lack of cam lubrication... the cam still sits up high, out of the oil, and without a direct oil path so it still has the same potential to corrode if left sitting for some period of time.  

 

I did opt for the drilled cam mod for my overhaul, and I'm going to add a pre-oiler as well, so hopefully I'll oil much, much closer to the cam lobes before I turn the key.  Hopefully that helps longevity, but only time will tell.  It is just a band-aid to help a design defect IMO.

 

Just get one of Phillips thing a ma jigs to turn things on and off, hook that sucker up to a relay and have it fire the pre oiler remotely. Or better yet, just get a 24 hr timer to fire it every day for about 30 sec's. Keep that cam coated.

[DaV8or]

Just get one of Phillips thing a ma jigs to turn things on and off, hook that sucker up to a relay and have it fire the pre oiler remotely. Or better yet, just get a 24 hr timer to fire it every day for about 30 sec's. Keep that cam coated.

 

Not a bad idea. Anybody here have one of these pre oilers? How does that work?

[pinerunner]

Can you see ALL the cam lobes via a borescope up the oil drain? That could be powerful and easy!

Maybe I missed something, but why not simply replace cam, lifters and rings? Then go on your way for the next 1000 hours or so. 

 

I chose a Firewall Forward "drilled camshaft" for my engine. So far, the lobes look great (via borescope up through the oil drain) and no significant iron in the UOA's. 

 

[KSMooniac]

NIce idea, but it won't really work because the "intake" hole on the cam for the oil is only a hole at one location, so it picks up oil every revolution...it is not a continuous supply that could oil the lobes without engine rotation.  The pre-oiler will only guarantee that the oil supply is ready to be pushed into the cam before you turn the key, and of course get the oil out much quicker.

[aaronk25]

So bottom line, does this engine have 1700 since overhaul? Aren't a lot of those hours before you bought the plane? As far as cause of failure...You will never know as the majority of the engines life was not supervised by the current owner. The newer engines with roller tappets don't have the experience/data points yet to know how "much better" they are. Time will tell.

When you inherit an engine there are a ton of unknowns. That it failed on the last quarter of a run to TBO while on the current owner/operators watch while doing "the right stuff" is of minor consequence. All this discussion is conjecture. Talk to the original owner and find out how he/she flew/maintained the plane...

Yes, I understand that there was a gear up and some repacements (engine parts) were made...Wasn't a major. Mix/mash. This is the result I would expect after 300-500 hours with a mystery higher time since major engine with field replacement of parts.

Hi Scott,

Your right I am second owner. A few months after Bolduc completed the prop strike inspection, I called him and he explained that he checks the parts inside the case to make sure they meet service tolerances. Aside from maybe a valve sticking because of the previous owners rich operation, I don't think there is any other scenarios of previous operating techniques that would shorten the life of the new cam and lifters (whoops I said it I mean reground new to me lifters).

I'm leaning the reman route, just wish lycoming would let me have a stc'd oiler cam put in too. It's amazing they are so regimented that they won't allow items to be deleted such as mags ect on a factory reman, let alone a different cam. I'd like to add the electro air ignition to the new motor since I spend a lot of time up at 10-15k...

The combination of pressure lubed cam and roller would be awesome.

[aaronk25]

NIce idea, but it won't really work because the "intake" hole on the cam for the oil is only a hole at one location, so it picks up oil every revolution...it is not a continuous supply that could oil the lobes without engine rotation. The pre-oiler will only guarantee that the oil supply is ready to be pushed into the cam before you turn the key, and of course get the oil out much quicker.

Anything is better than what we got......anyone know what rotax does?

[cujet]

Can you see ALL the cam lobes via a borescope up the oil drain? That could be powerful and easy!

 

Yes, you can eventually get to all the cam lobes. However, the sump and the crankcase are separated by a narrow slit formed by both case halves. You need a 5mm or smaller borescope to do this. And, it's exceedingly difficult to position the borescope, the crank and the viewing angle properly. Looking at all 6 lobes is an all day affair for me. 

 

Look at the picture of the case half. Look where the sump bolts on (on the upper right of the picture) . Imagine that when both case halves are together, there is precious little room to work a borescope up through what are narrow passageways. 

 

[cujet]

Anything is better than what we got......anyone know what rotax does?

Rotax cams are located on the bottom. I believe they also have a 8 lobes (but I've never seen a Rotax cam) . The Lycoming has 6 lobes. In other words, the Lycoming has 2 lifters on a single lobe (the opposing left and right cylinders share an intake cam lobe) . 

[jetdriven]

Often the cam lobes look fine, it's the lifters is where the problem starts. Mine had 3 lifters fully spalled, but the lobe where the single lifter went bad was shared by the opposite side , and that lifter plus that cam lobe was fine.

Another thing, to see the whole lifter face you have to remove the pushrods and push the lifter back off the cam lobe. I just did this on the rear two cylinders of my boss's Piper arrow. We had to change a cylinder anyways and I took a good hard look. It was a Mattituck overhaul in 1989 with 2300 hours on it. Straight aeroshell W100, no additives and it sits in Houston sometimes 60 days before flying. I'm talking 25-30 hours per year. What gives?

[Alan Fox]

Its a shame , on continentals you can replace lifters without splitting the case....

[carusoam]

CUJ's photo wins a prize for great detail and focus!

Best regards,

-a-