BCP experts - looking for A&P's/engine builders input. I may end up with an airplane that has an O-320 original to the airplane in 1956. I has 100SMOH in 1976. Pickled at some point shortly after and revived in 2012. Cylinders scope good but probably going to spend the money to pull a cylinder to get a look at the cam etc.

Question - assuming no corrosion since it's in a dry climate and it is currently flying and not making metal, what other concerns might there be?

Question - assuming no corrosion since it's in a dry climate...

I'm not an engine builder, but I'd say that's one HELL of an assumption for a thirty-year-old engine...

TxAgfisher wrote:Question - assuming no corrosion since it's in a dry climate and it is currently flying and not making metal, what other concerns might there be?

Rubber hoses and gaskets. Insects and bird nests.

I may not have clarified, airplane is and has been flying the last 4 years.

I know engines that have set longer, but you still need to price in some deduction. How much...that's between you and the seller. The way I'd do it to feel comfortable is exactly what you've stated. See if the seller will let you pull a cylinder and look inside for corrosion. Also, since it's been flying for four years, see if he's been doing oil analysis. Filter or screen? How many hours has it flown per year in the last 4?

Like Hammer mentioned....don't assume anything. The climate is just one of many factors. Oil acidity, oil adhesion to parts, etc. Too many variables to assume anything over those years...gotta dig in and put a knowledgeable set of eye balls on it.

Good luck!

Its a very positive sign to see it has been flying for the last few years, I would also be interested in seeing the leak down results and oil analysis if it were done since it was brought back. I wouldn't be too concerned with an old engine, I have brought them back after sitting 25+ years. Sometimes they need a little going through, my current airplane was sitting for nearly 30 years and if you dig through some previous threads I made I was initially having some issues with it that turned out to be weak valve springs. Remember an engine sitting for that long was sitting with at least some of the valve springs compressed so they may be a little weak.

Other than that I would just pay close attention to rubber items like hoses/o-rings/seals.

Oil analysis on an engine which doesn't get run will tell you nothing. The internal corrosion will be the key. I agree that rubber hoses and gaskets will be suspect.

Many of us are running around on cams, cranks and crank cases that are also 35 years old, they've just been "overhauled" a few times and returned to service.

If the engine was pickled correctly until 4 years ago I wouldn't necessarily run away crying. Just make sure you price the deal so you can handle a setback or two.

It hasn't had an oil analysis that I am aware of but it's only been flying maybe 15-20 hours a year. Screens and spin on filter have been monitored and no metal has been found. Price reduction is being negotiated but it wouldn't be enough to make up for a quick overhaul.

I have a call out to Lycoming waiting on the sales rep to call me back to make sure it's at least worth core value.

FWIW I am running a Franklin 165 with just shy of 1000hrs SMOH from the early 60's. It doesn't make metal and the cylinders are in the low 70's. It runs silky smooth. My plan was to run the engine to at least 1200hrs before I do an engine upgrade, at this point, I have no reason to believe I won't make it.

If you wanted to buy it and it literally hasn't run in 35 years, this is what I would do*:

Get owner's permission to do the following.
Get an experienced *engine* mechanic to accompany you, unless you are one. Not a run of the mill aircraft mechanic, an engine shop guy.
Bring a borescope, mirror on an extendable stick, basic toolkit.
De-cowl the plane, drain the oil and pull the drain valve, pull the plugs and rocker covers.
Pop the governor (if applicable), magnetos, mag drive gears (remember what angle they were at!) and throttle body, inspect all you can see for corrosion.
Inspect all you can see.
Inspect the cam and crank as best you can via the oil drain and filler holes. Inspect the accessory gears through the magneto holes.

You'll be up for re-timing the engine and a few hours labour, but I would never buy it without doing some serious inspection like this.

If you want to pull a cylinder, even better.

Unless you're very lucky, I would bet something is rusted to hell. Either that, or everything metal will be totally fine apart from a light patina.
If anything is rusting continually, 35 years is long enough to make a real mess of whatever part is corroding away.

Any plastic and rubber seals will probably have perished / vulcanised / degraded in some way during that time. The seals at the front of the crankshaft for instance, they might not be in good shape. Also the rubber bits around the pushrod covers. That is the other main thing I can think of.

* I am not an engine expert, just a home-builder / mech engineer.

I bought a Maule M5 220c which sat for 30 years with only 187 hours on it. Beyond mouse urine corrosion in the right wing which ended up requiring a new main spar, nose ribs etc., my engine builder pointed out to me that all the bearing surfaces had been contacting the same exact points the entire time. His explanation was that this can change the surface hardness of the contact spots and lead to bearing failure.