Ask Paul: What should I do with an engine that hasn’t been flown in years?

Question for Paul McBride, the General Aviation News engines expert: I bought an airplane in the summer of 2022 and have not been able to pick it up yet due to a lot of work and a rusty pilot situation. This aircraft has been sitting outside in New Hampshire.

The mechanic ran it once about a year ago and sprayed the cylinders with Marvel Mystery Oil.

I plan on retrieving the plane after I do the annual sometime in May.

As I’m not very familiar with a flat engine, here are my thoughts, concerns, and proposed actions:

1. I would like to pre-oil the engine with some hot oil but I don’t know if it has a pre-oil port or where it is located.
2. I would like to take a cylinder or two off to check the tappets and cam and if they are OK, liberally oil them by hand and brush, and maybe the cylinder walls on the crank side of the cylinders that were not removed.
3. Remove all rocker covers and oil mechanisms liberally.
4. Remove the spark plugs and oil mist cylinders through the spark plug holes.
5. Possibly lubricate the crank shaft where it exits the case with 10W oil to possibly lube the seal.
6. Is there a way I can lube the accessory section gears, bearings, etc?
7. After the pre-oil and lubrication of parts, I plan on removing the spark plugs, then rotating the prop by hand about 6 blades, then motoring the engine until I see a rise in oil pressure, then continue for about 30 seconds then stop.

Paul, what do you think of the above actions?

I’m also thinking of changing the fuel pump. Can I put on a newer style pump or does it have to be the original style? The original pump has 1,801 hours and has never been overhauled.

I’m also thinking of changing the carburetor. The engine has Slick mags. Oil is Phillips 20W-50.

What do you think? What would you do and how would you approach this situation?

Tony Wiser

Paul’s Answer

So, you bought an airplane in the summer of 2022 and have not been able to pick it up yet, and now you’ve got some questions.

I guess that makes us even then, because I’ve got some questions too.

My first question is whether you’ve reviewed the past maintenance history of this aircraft? Hopefully, the logbooks will be well detailed and provide information about how this aircraft has been operated and maintained.

As you know, extended periods of inactivity are one of the worst things for any mechanical device, so check the history closely to see what it tells you.

As an example, infrequent oil and filter changes could be a bad sign and possibly serve as a warning as to what you may find when you are actually inspecting the engine.

The idea of pre-oiling any Lycoming engine won’t accomplish what you think it might. Pre-oiling is only going to provide the warm oil that you intend to use to go only to the areas that receive pressure oil. This is fine because that will do all of the main and connecting rod bearings and also the camshaft bearings.

The big problem here is that it will not lubricate the critical area between the tappet body and the camshaft lobe since this area is only lubricated by splash oil when the engine is running.

By the way, there is no pre-oil port on the engine.

So, let’s look at some of the other things that might be considered suitable to get the engine ready for being returned to service.

I’m not happy that the mechanic ran it up about a year ago because ground run-ups are not sufficient to bring the oil temperature up high enough to boil off the contaminates in the oil, but that’s water over the dam, so we can still proceed to make certain the engine is fit for service.

Your idea of removing two cylinders is a step in the right direction.

My suggestion would be to do a close visual inspection of each cylinder using a borescope. Depending on what you find — and I suspect that you’ll find corrosion in the cylinders — I would remove the two cylinders showing the most corrosion or, preferably, the #1 cylinder, which is the right front as seen from the pilot’s seat, and the #4 cylinder, which is the rear cylinder on the left side of the engine.

This will provide you with an opportunity to visually inspect the cam and tappet surfaces for any signs of corrosion or pitting on either surface.

Needless to say, should you find corrosion in this area, then your decision is made for you, and you can prepare to spend some money.

Let me back up a bit and make a few suggestions assuming you don’t find corrosion in the cylinders.

When removing the cylinders, I’d recommend that the mechanic pull the cylinders off, but do not pull the piston out of the cylinder. Just remove the cylinder far enough to enable the removal of the piston plugs and piston pin.

My reason for suggesting this is because if you remove the piston from the cylinder and find the engine can be continued in service, you’ll have to hone any of the cylinders where the piston was removed and install new piston rings.

Let me cut to the chase. I don’t find anything on your list that I can find any real fault with, but to be honest, I think what you mentioned is way overboard — unless you know something that you failed to mention.

I see no reason to replace the fuel pump or the carburetor until you’ve actually completed the things mentioned previously.

Your mechanic will be your best source of information and if you are unsure of the local mechanic and his expertise, then inquire about someone who is familiar with the make and model of the aircraft and get him to do the inspection. Spending a little money this way may save you a lot of money later on.

Once you’ve confirmed that the engine in not full of corrosion and everything is reinstalled, then you can pre-oil the engine by motoring it through using the battery with mag switches off. Pulling the prop through by hand will do no good because it can’t be done fast enough for the oil pump to provide enough pressure to move the oil through the engine.

From reading about your situation and checking your list, I believe you have enough common sense to work through this challenge and will do everything possible to see that this aircraft can be safely returned to service.

I wish you good luck and many happy hours of fun in your new aircraft.