Premature Camshaft / Cam Follower failure

I have just spoken to a highly reputable engine shop in the USA, whose boss I know personally

Their view is

• there is no evidence of defective camshaft or cam follower metal in Lyco engines
• most camshaft related failures are the result of corrosion of the camshaft, which then destroys the followers
• some camshaft related failures are the result of corrosion of the followers, which then destroys the camshaft
• flying for 1 hour is not enough to boil off all the water from the oil (the cruise oil temp is well below 100C)
• flying school engines usually make TBO without a single speck of rust, because they fly regularly
• sitting in a heated hangar makes no difference to engine corrosion
• standing around for a few months is a dead-cert corroded engine
• the only sure way is to have dry air (some form of aircon)

Reputable or not, this clearly is not true and not supported by any evidence. There are lots of engines flown irregularly for decades and without major problems with the camshaft or lifters. Then there are engines where after a few hundred hours in a few years, the lifters are badly pitted.

I agree that getting the water out of the crankcase has to be very beneficial and this is why I built this contraption to push relatively dry air into the crankshaft. Just open your oil filler neck after a flight and watch the water vapors. That’s the source of corrosion.

An engine that does not fly regularly still has water in the crankcase every minute it is on the ground. The source of the water is the combustion itself and due to the monkey technology it leaks through the piston rings into the crankcase.

not supported by any evidence

The problem I see is that there is always a possible third factor which can mess up the conclusions.

• unless you owned the engine from new, you don’t really know its history (logbooks from another person are like a P&L account )
• an engine “running fine” can be full of rust and since it won’t be opened until big pieces are found in the filter(s), you aren’t likely to ever be in a position to make a connection between the usage pattern and the rust which is found under the next ownership
• tests have shown that a 40% loss of cam lift reduces power by only 10% – most renters and many owners will never notice that
• flying logbooks cannot be practically independently verified (serious legwork, and then possible only if flying between full-ATC airports)

So, this can lead to a scenario where somebody has been flying frequently yet his engine disintegrates. The logbooks show regular usage from Day 1 but may be forged (everybody nowadays knows that a hangar queen aircraft is going to be seen with suspicion) by having been rewritten from scratch.

It’s a bit like doing social research. In this case, the population size is always very small but third factors are plentful.

Personally I would find it surprising that Lyco would put crap metal into a $50k engine and continue to do it for years or decades – especially after the FAA nearly shut them down following the crankshaft saga where a subcontractor left out some heat treatment stages. Cam followers cost maybe $50 each to make. Camshaft maybe $500.

Personally I would find it surprising that Lyco would put crap metal into a $50k engine and continue to do it for years or decades – especially after the FAA nearly shut them down following the crankshaft saga where a subcontractor left out some heat treatment stages.

All I see is that the FAA gave Lycoming the mandate to rip off thousands of its customers by forcing them to pay thousands of dollars to fix engines that were not airworthy from day one. I would love for something like this to happen to my business.

Also there are a lot of aircraft that do not change ownership in 20-30 years where the same owner performs multiple overhauls. This “don’t fly = corrosion / fly often = no corrosion” mantra is not true, no matter how often people keep repeating it. There are both a large number of aircraft flying very often but having lifters/camshaft fail prematurely and there are aircraft sitting in humid hangars for decades and showing no problem in service and normal wear on overhaul.

Peter, I think yours is a pretty intelligent assessment but I would take issue with this statement from the engine shop:

standing around for a few months is a dead-cert corroded engine

A great many aircraft engines have sat around for months over the years and suffered no ill effects, despite the somewhat psycho European obsession with the issue Most aircraft over the years go into and out of frequent use. What I think may be true is that if they sit around in a very humid environment (high relative humidity) for months they may suffer from corrosion, which may cause cam problems. I don’t think any of that potential is dead certain.

Eventually on one of those cycles the ambitious new user decides to overhaul the engine.

All I see is that the FAA gave Lycoming the mandate to rip off thousands of its customers by forcing them to pay thousands of dollars to fix engines that were not airworthy from day one.

The effect you describe I agree with (Lyco ripped off a lot of people) but the method was an unfortunate abuse of the certification process, under which the granting of an engine TC by the cert authority removes the mfg’s authority to mandate SBs (only the cert authority has that power) which protects the consumer from abuse (like what happens in Europe where SBs are often mandatory…) but still allows the mfg to hide behind the 12 year official engine life for litigation (product liability) purposes.

Lyco then skillfully avoided a class action by putting a 12 year life on the crank (for which an AD was imposed, playing nicely into their bank balance) but offering a free replacement crankshaft if you go to them for your overhaul They are under no obligation to support 3rd party engine shops so “you Sir” suffered zero economic loss…

And those who sued, or credibly threatened to, got a deal, under an NDA so tight that even people I know pretty well did not say a word. I reckon there must have been liquidated damages in that NDA, and most of them didn’t know that is unenforceable (in the UK) beyond actual losses to the party relying on the NDA.

What I think may be true is that if they sit around in a very humid environment (high relative humidity) for months they may suffer from corrosion, which may cause cam problems. I don’t think any of that potential is dead certain.

So, what can be different about Europe? I would say that a much higher % of engines in Europe are exposed to humidity than in the USA (or Africa, etc). Most of Europe (well, where any GA takes place) is pretty damp. All of the UK is very damp. All of continental Europe is damp. But the USA has large swatches of dry air – basically much of the “middle bit”. In Arizona the temp-DP spread is mostly massive – around 30C IIRC. The RH must be in single % digits most of the year. I did my IR there and remember this.

So, what can be different about Europe? I would say that a much higher % of engines in Europe are exposed to humidity than in the USA (or Africa, etc). Most of Europe (well, where any GA takes place) is pretty damp. All of the UK is very damp. All of continental Europe is damp. But the USA has large swatches of dry air

Sure, that’s a fact.

Has anybody produced data or other technical explanation for how trace corrosion on cam/lifter surfaces would produce the kind of wear that’s observed?

I would share the idea of wrong steel combination in Lyco valve gear. Similar problems exist in some car engines but not universally . In our 64 Jag E-type DOHC there was never any trouble with worn cams or cup tappets. And she sits very long times in recent years, last year only two trips, to TÜV and once to the airfield in an unusually warm February. Then the 1985 OHC Ford that required changing the cam and lever followers at least once despite being used several times per week. Wear was only finally dealt with by welding high chrome material on the followers – and that should be an orientation for Lyco etc. . It does stop corrosion as well . Hardness is not the only factor to prevent wear, it is the material combination in friction partners ! Vic

Both the cam and the followers are case hardened (nitrided) but I don’t know to what depth.

Once the nitrided layer wears through, wear will become very rapid.

Lycoming have zero incentive to improve their engines. Cam/follower wear is post warranty. All it does is increase their revenue. With only two vendors of equally poor products, the market mechanisms just do not work.

Imagine Volkswagen had decided that fixed time magneto ignition and manual mixing control is safer and therefore they will stick to it as it’s the perfect solution. They wouldn’t be around anymore. Why? Because they have fierce competition.