Back when in college I worked in a lab performing corrosion studies on steel aircraft parts that were bathed in various aviation oils. Most people would be surprised how fast corrosion spores form and how numerous they can be while remaining undetectable to the naked eye.

A visual inspection is better than nothing but you can pretty much count on problems if an engine has been sitting and not stored properly.

Thanks for all the info people, good stuff.

Troy Hamon wrote:This is why I actually prefer to purchase a runout engine when I buy a plane. The owner knows the engine value is nil, and I don't have to negotiate from a point of different views of whether the engine is a risk or not. And as the buyer, I know going in that I am dealing with a likely engine overhaul or replacement, and any extra hours I get out of the engine before it starts showing signs of wear are just bonus hours.

I like this, from a buyer's perspective. It puts the engine's future solely in your hands as the next owner.

On the other hand, sellers can vary. "Yeah, it's got 2000 hours on it, BUT IT RUNS GREAT!"

Quick update, owner and their mechanic were SURE there would be no corrosion on the lifters/cam so the agreed to pull the front left cylinder (the one everyone told me gets you the most access) and also look in the accessory case. Sure enough, spalling on #2 lobe and lifter. I'm sure they now wish they hadn't let me pull the cylinder now and I genuinely feel bad for them since the engine likely would've ran just fine for many hours to come.

The airplane is an unlisted gem so I'm now negotiating on the cost of work that it needs, I don't mind pitching in a littl. Got a quote and the price isn't bad but I hate long lead times especially when I really want an airplane. I actually don't mind that this is the case, gives me a little more peace of mind that it won't eat the cam in 100-200 hours.The rest of the airplane has been completely restored so getting the engine in tip top shape will complete the whole thing.

Thanks to everyone for the help.

I just did a prebuy on a Helio that ended up the same way. Engine sat for 7 years and the owner was sure he had it pickled properly. But there was already previous damage. Tappets showed pitting and cam had wear from said pitting. Unfortunate for all parties involved. Hard to see the putting in the picture, but you can see the wear on the cam lobe.

Bottom line: If it’s a Lycoming, it’s set for a long time without being properly pickled, it’s going to almost certainly have cam or follower corrosion.

Buying a Hangar Queen? Plan for a cam and kit.

MTV