Is DLC Lifter Coating the Cure for Lycoming?

[MBDiagMan]

5 hours ago, mike_elliott said:

Actually, there are planes that have been flown regularly that had cam and tappet part numbers show up in the suction screen. CarolAnn Garratt's J was flown weekly for hrs at a time and needed a new engine at about 1400 hrs from cam and tappet disintegration. Cant blame corrosion on this one. If it is corrosion causing the problem, why would LYC fix the effect (DLC tappets) instead of fixing the problem? I know, conspiracy theory. None of this first principal thinking allowed.... back to our group think Florida is bad for Mooneys..

 

Okay, I’ll bite.  How do you, as the engine manufacturer, propose solving the corrosion problem in a method other than taking steps to make components less susceptible to corrosion?  

[mike_elliott]

direct cam lobe/tappet lubrication, direct valve lube (bravo mod comes to mind), metallurgy consumerate with the required function would be a start over the "lets splash some up thataway and let some run down a pushrod tube to get to the valves from the hydraulic lifters" approach.

Absent wanting to redo the lubrication system, perhaps roller cams....oh wait....

 

[carusoam]

Looks like we have two choices... for improvement, not a cure...

DLC...   on the existing engine design....

Roller cam followers...   need an updated case design to match...

 

In the spray oil everywhere we have the Ney nozzles...  named after the guy who built them... Chuck Ney...

A few have gotten loose inside the engine....

 

Putting oil directly where we want it... comes in the form of a cam modification....  centrilube cams...

 

A big challenge... is dry cam surfaces... the unlubricated surfaces get damaged when dry parts are sliding past each other...

Crummy news... it isn’t just Lycoming or Continental... both have shown cratered cam followers and metal in the oil filter...

 

Fly early and often, pray to the gods of cam and follower metallurgy....

Go Turbine!  Avoid the whole cam issue... 

Best regards,

-a-

[MBDiagMan]

8 hours ago, mike_elliott said:

direct cam lobe/tappet lubrication, direct valve lube (bravo mod comes to mind), metallurgy consumerate with the required function would be a start over the "lets splash some up thataway and let some run down a pushrod tube to get to the valves from the hydraulic lifters" approach.

Absent wanting to redo the lubrication system, perhaps roller cams....oh wait....

 

Read post number 14 in this thread written by ArtVandelay.

[mike_elliott]

45 minutes ago, MBDiagMan said:

Read post number 14 in this thread written by ArtVandelay.

I have, thanks for reminding me to reread it. I havent seen this statement from Lycoming, only here from Art and if true (and I am not saying it is not), Lycoming is imply their metallurgy is a solution. It begs to question why a lot of old classic cars whos overhead cams not sitting in oil that only get fired up once every year or so dont swallow their cam lobes and tappets and just what technology existed then that prevented this? Perhaps engineering. Granted the technology might not have existed in the late 30's. By hardening the surface of the tappet, the cam lobe inherits more of a role of the sacrificial surface caused by any friction.

Without direct lubrication, their will be friction, and even then.

 

[ArtVandelay]

I have, thanks for reminding me to reread it. I havent seen this statement from Lycoming, only here from Art and if true (and I am not saying it is not), Lycoming is imply their metallurgy is a solution. It begs to question why a lot of old classic cars whos overhead cams not sitting in oil that only get fired up once every year or so dont swallow their cam lobes and tappets and just what technology existed then that prevented this? Perhaps engineering. Granted the technology might not have existed in the late 30's. By hardening the surface of the tappet, the cam lobe inherits more of a role of the sacrificial surface caused by any friction.
Without direct lubrication, their will be friction, and even then.
 

I was told DLC is extra slick (like teflon pans), even without the oil film.

[A64Pilot]

I think something has changed since the original design. I know fuel chemistry is different, but I don’t know how. 

Automobiles went to rollers because the oil formulation changed and ZDDP wasn’t allowed at high levels anymore because it poisons convertors.

 Some of us run Diesel engine oil in our cars to keep the ZDDP.

Anyway it would seem that ZDDP would be the answer, but it can’t be that simple. ZDDP is not ashless

‘So did the way the parts are Nitrided change? To a more environmental friendly way? Inkwell Cadmium plating is getting harder and harder to do, I assume there is none done in California.

But Lycoming’s didn’t eat cams before that 172 engine and it seems soon after, they all started losing cams.

[MBDiagMan]

11 hours ago, mike_elliott said:

I have, thanks for reminding me to reread it. I havent seen this statement from Lycoming, only here from Art and if true (and I am not saying it is not), Lycoming is imply their metallurgy is a solution. It begs to question why a lot of old classic cars whos overhead cams not sitting in oil that only get fired up once every year or so dont swallow their cam lobes and tappets and just what technology existed then that prevented this? Perhaps engineering. Granted the technology might not have existed in the late 30's. By hardening the surface of the tappet, the cam lobe inherits more of a role of the sacrificial surface caused by any friction.

Without direct lubrication, their will be friction, and even then.

 

Flat tappet auto engines DO have such problems, in spades, especially after the oil providers removed the ZDDP additive, so necessary for flat tappet health, without telling anyone.  Many old cars that are only run occasionally do exhibit such problems, but they often go unnoticed.  Do you know anyone with a classic car that cuts their filter at least once a year?

[A64Pilot]

Not to be argumentative, but older cars with flat tappet cams that are well broken in usually do OK. The real issue comes from rebuilding a car with a new cam and lifters, that’s most often the worst case, add in stiff valve springs because it’s a hot rod motor and without ZDDP your going to eat a cam most likely.

Older spec Diesel oil still has the ZDDP, but as newer Diesels have catalysts the ZDDP is going away, the latest Diesel oil spec is pretty much only for new modern Diesels with catalysts, and of course they have roller tappets, and other than the lack of ZDDP, there is no real reason for that as they don’t have radical cam profiles or high revving.

‘ZDDP is readily available as an additive, but be careful as if you exceed 1400 PPM or so of it it accelerates wear of the cam. So only add to enough to achieve about 600PPM as most oils have 600 to 800 PPM to start with.

‘ZDDP protects from wear, corrosion and also as it’s zinc it helps neutralize acids. It reacts with the cam and build up, and is sheared off, called sacrificial lubrication.

However it’s not ashless, so for a motor that burns a lot of oil it can build up deposits in the combustion chamber, these deposits can be a source of ignition and that can cause detonation.

It is NOT approved for aircraft.

Shell Rotella T6 which can be had as a 5W-40 or 15W-40 is a synthetic Diesel oil and has 1200 PPM of ZDDP, it’s an excellent oil for classic cars with flat tappet cams. It’s a tiny bit shy of the ideal 1400 PPM, but Shell likely knows what they are doing and has it right.

 

Edited May 26, 2021 by A64Pilot

[mike_elliott]

1 hour ago, A64Pilot said:

Not to be argumentative, but older cars with flat tappet cams that are well broken in usually do OK. The real issue comes from rebuilding a car with a new cam and lifters, that’s most often the worst case, add in stiff valve springs because it’s a hot rod motor and without ZDDP your going to eat a cam most likely.

Molykote G is an engine builders friend on tappet surfaces. Used it since my first race engine build in 1968

[A64Pilot]

I think Crane cam kits came with the moly, but of course it stays for a short time only.

[carusoam]

Really important question...   

How do I know if my ‘95 firebird LT-1 has roller cam followers..?

Its been sitting idle long enough....

Best regards,

-a-

[mike_elliott]

13 hours ago, A64Pilot said:

I think Crane cam kits came with the moly, but of course it stays for a short time only.

 it bonds to the metal long enough to allow the tappets and cam lobe to break in and seat together. Engine revs have to be high to properly break in the 2 faces initially, as high spring loads will really play havoc on the surfaces if allowed to spend extra time applying pressure at low RPM's. A good engine builder of course knows this and will break in accordingly. This initial break in period is where most significant cam/tappet wear will occur, and a lot of people protect the much cheaper rod bearings at the cam lobe expense. Dry faces anytime isnt good, but especially before they are seated together. Splash lubrication is sub optimal at best, especially with a thick oil that may not flow well until its viscosity thins enough from engine heat. Never mix up a lobe and its tappet when reassembling if torn down. Again, engine assembly 101

[JimB]

Pretty good article but it doesn't provide much in answers other than infrequent flying is not necessarily a cause for cam/tappet corrosion and wear...

https://www.aviationconsumer.com/maintenance/the-cam-problem-corrosion-failures/ 

Weiss doesnt necessarily buy the standard explanation that infrequently flown engines are subject to corrosion and since flying hours are down, rust is up and thats whats causing the problem. “I just dont see a pattern here. We see cam failures in engines that are flown a lot, in engines that arent flown much, in airplanes that are hangared and not hangared. Even in some flight school airplanes,” Weiss told us

[A64Pilot]

15 hours ago, carusoam said:

Really important question...   

How do I know if my ‘95 firebird LT-1 has roller cam followers..?

Its been sitting idle long enough....

Best regards,

-a-

95% sure if it’s stock, it has hydraulic rollers

[MBDiagMan]

Yes, the roller lifters came along in the SBC in ‘87 or ‘88.  My ‘88 L98 Vette had them.