How to Preserve a Lycoming for a few months - help!

I think what corrodes things is high humidity (temperature and dewpoint being too close) combined with a lack of surface protection.

You see this with machine tools. Lots of hobbyists have a drill, a lathe or even a milling machine, in a shed in the garden. And all that stuff has large precision ground surfaces, which go rusty fast unless covered with oil all the time. Garden sheds are death to all tools, even things like pliers, unless heated to provide a decent separation between temp and DP.

As to the "rust " problem with Lyco cams I have yet to see some more components from those engines with typical rust traces. There are more parts inside than just cams that should corrode as well – if ever real rust was cause for severe wear on cams. So as long as nobody can supply photos – I do not mean cylinder bores with red stains, different environment here – of rust on conrods, cam follower faces around the outside of the convex contact face, valve train gears or some such parts, I cannot see rust much of a factor for cam problems. Minor surface imperfections on cams should not be responsible for much wear, the oil film should cope with that . But really I believe the minimal remains of oil after long periods of hangarage and almost dry lobes especially when using multigrade will start friction wear very soon and will lead to a lot of wear in short time. Certainly the material choice for cams and followers plus heat treatment is another factor and nobody can say what has definitely gone in decades into production or in your particular engine. The poor point-like contact patch with new cams and followers does not help in the drama when convex and taper ground shapes are mated, a bit of wear will form faces for better fit soon. But when lubrication before starting remains questionable for long times that wear will rise to unacceptable levels and defects on valve train. A pre-oiler for the camshafts would be great , got some ideas for that but no chance you´d pass that in annuals on certifieds I guess. Rust on machine tools is not so clear cut, depends on the storage conditions of course, but also on the “human touch” : There are persons who produce rust on plain steel the next day you look just by touching the machine, sweaty hands. One thing you have to watch with garden sheds: When many days of cold weather are ended by sudden vey warm days you will keep doors CLOSED else you will get dripping wet heavy machinery from condensation of moist warm air on cold surfaces. At home I don´t have much of a problem in unheated workshop or garage when being aware of that condensation, an electric heater for machine jobs in winter is allright – but then I got a 500 kg lathe in second floor under the roof in a heated room, so not often a need for heating that workshop or a desire to go there. Allright, it was quite a thing to disassemble the lathe to carry it up two stairs in big lumps and get it together in perfect fit – but adviseable when China type lathe, you´d find details you like to work over a bit to your liking in the ocasion. Vic

You may be right Vic but engine shops also report camshaft damage due to rust and presumably they can see where the rust was.

One pilot on here, a syndicate, got a “disintegrated” engine, rust assumed due to a long “hangar queen” time before they got the plane (the usual scenario), and they got the metal lab-analysed and found it perfectly to spec. I have seen the report. I tried to get him to consent to publishing it but it seems his syndicate would not agree. Hence I don’t believe the “Lycoming using crap metal” theory, even when it is definitely true on other occassions e.g. the crankshaft saga some 15 years ago (that one was a complex story, with missing heat treatment stages (probably annealing) being the main culprit, but those cranks snapped within hours, IIRC).

Here’s a couple of cam followers with 700hrs on them, my IO540. They came out when the crank was done, in 2008. Whether there was rust there at some point, nobody can tell, but it is known that Socata stored a load of engines for years and some rusted badly before being installed in planes. My engine had rust in the bores below the piston travel – article here.

Very true about sweaty fingers on machine tools

This might sound like a silly question but why can’t you just replace the oil with fresh and put enough in to cover the cam?

You would have to completely fill the crankcases. Yes that would work. I read somewhere that Spitfire engines were stored like that at one point. A lot of oil though – maybe 50-100 litres?

Lyco engines have the camshaft at the top of the crankcase.

Would you even need to use expensive aviation oil? Wouldn’t some first cheap supermarket car oil do the trick?

Yes, but something really wrong might damage oil seals, especially the front crankshaft seal. Straight aviation oil is also cheaper than any decent car oil.

There is the Centri-Lube camshaft STC. I don’t know if there is an EASA version of the STC but probably yes. In fact that thread is worth a read as directly applicable.

A couple of observations here:

I read in this thread that the engine oil has been drained out. You should not leave an engine for long periods without the correct amount of oil in the crankcase because it’s possible to cause air-locking in the oil pump which will stop the flow of oil when you refill and come to start up the engine. Occasionally, the air lock is very difficult to move. Suggest you at least keep the engine filled with fresh oil and watch the oil pressure when you start up first time.

There are many types of corrosion at work in our engines. As in this thread, the main one talked about is an engine left idle for long periods in a damp atmosphere causing rusting and pitting. There is chemical corrosion going on, galvanic corrosion and electrolytic corrosion all playing their part. Some years ago I was in dispute with an aircraft manufacturer who supplied me a new aircraft with a heavily corroded engine straight out of the factory. I had parts of the engine analysed at Newcastle Universities corrosion analysis department and they were very scathing about the mixture of materials used in Lyc and Conti engines. Mating dissimilar metals were definitely contributing to electrolytic corrosion within the engine causing pitting, for example between a cam lobe and a follower. The best defence we all know is to run these engines often, use as many oil additives as you can get to help such as Camguard and keep the aircraft in as dry an environment as possible.

A common misunderstanding is to think the hangar has to be warm. I doesn’t. What it needed is to minimise the rate of change of temperature. That’s when condensation occurs which becomes the electrolyte for further corrosion. Condensation is the killer. Problem is very few hangars have any heat sink so the rate of change of temperatures is huge so you get condensation.

In this specific situation in this thread, if I was facing another couple of months (in the depths of winter) before one can fly the aircraft, I’d definitely follow the storage/inhibiting guidance from Lycoming. Buy the correct storage oil (forgotten what it’s called) and follow the inhibiting procedure. Disconnect the battery completely (not just by the master switch). Then you know you’ve done the best you can and you can sleep at night.