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Have cam failures in Lycoming engines always been a problem?


nels

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On 7/3/2018 at 9:36 AM, nels said:

This has been a question in my mind since getting involved with Mooneys several years back and hearing about all the cam failure problems and everyone’s perception of why it happens.  Being an old car nut, along with a Mooney nut, I am aware of the auto industry totally moving away from flat tappet cam shafts and onto roller type cam shafts and the reason for the move. Lycoming has also moved to roller cam shafts. The additives of zink and phosphorous have been removed from motor oil mainly due to them not getting along with catalytic converters. The zink is a high wear and extended corrosion additive that is especially useful with dry starts with metal to metal contact. In particular with flat tappet cams. Our Mooney’s often sit for long periods of time allowing most if not all the oil to run off the cam and lifter surfaces so they are often subject to dry metal to metal starts. The zink evidently doesn’t totally leave the cam surfaces over time and allows for lubrication needed during the initial dry cam start.....at least that’s how I understand it.

So, for those that get oil samples sent off and analyzed , when an oil sample is returned from a lab check, does it give the amount of zink or zddp in the oil?

Also, did Lycoming’s cam problems coincide with the oil industry’s time line of reducing or eliminating these additives in auto motor oil? Or have Lycoming cams been a problem since day one?

Here is an interesting article in the Hemmings Motor News blog: https://www.hemmings.com/blog/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/

 

I’ve been involved in Aircraft maintenance since the early 80’s.  The earliest ones I recall were the O-320H2AD engines installed in the Cessna 172N series, they had serious issues.  Lycoming LW16702 additive was a response to the issue.  There is an AD calling for its use as well as mandatory oil filter inspections.

Clarence

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2 hours ago, M20Doc said:

I’ve been involved in Aircraft maintenance since the early 80’s.  The earliest ones I recall were the O-320H2AD engines installed in the Cessna 172N series, they had serious issues.  Lycoming LW16702 additive was a response to the issue.  There is an AD calling for its use as well as mandatory oil filter inspections.

Clarence

Wow, 40 bucks for a 6 ounce bottle, what’s in it??

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Triphenyl phosphate. Basically forms a thin layer of corrosion when it sits and then that’s wiped off at startup.  

Thats why copper reads high on oil analysis when you use the Aeroshell “plus” oils. The TPP eats the copper flash off the gears and the cam. 

https://books.google.com/books?id=JEXnFqVTqJQC&pg=PA254&lpg=PA254&dq=triphenyl+phosphate+scuff&source=bl&ots=dSA7O0id4N&sig=n92M51EzzGvGxjUd-xUOd3Xp5b8&hl=en&sa=X&ved=2ahUKEwiptoTm-4bcAhWBhOAKHVrJAzoQ6AEwBXoECAMQAQ#v=onepage&q=triphenyl phosphate scuff&f=false

Edited by jetdriven
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My wife wants a new zink for the kitchen.  I told her we can just buy some cases of camguard instead :-)

My PCV valve on my honda engine recently failed and man I was burning some oil - all better now.

Interesting re the TPP additive's history / chemical engineering.

I'm also reading that the 76 series engines are the only Lycomings that don't need to be split to remove the tappets - didn't that come up in a thread a couple of days ago?

Time is a flat circle, etc.

It was interesting learning about Hertzian stress.

Whatever happened to Sacremento Sky Ranch - there must be a story.  They used to have fun stuff to read on their website.

I continue to digress.

 

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