Piston Engine

Overhaul Part

The end-result of overhauling an engine is a little anti-climactic. Sure, it's a kick to light it off for the first time and take off powered by an engine that you've had in hundreds of little pieces. If everything goes the way you want it, then the first flight of the new engine is as routine as can be. Which, naturally, is the desired outcome.

In my case, everything went swimmingly. The installation of the freshly overhauled engine was fairly simple--this is not a complex airplane--and there were no big problems. My philosophy with any piston engine overhaul is to consider everything forward of the firewall as fair game. No owner wants to have a major accessory problem within a short time period after the overhaul, so it makes sense to nip any potential problems in the bud to ensure maximum service life. My goal is to avoid any big problems through the next TBO cycle. This keeps costs down for the owner and increases reliability and safety.

So that is why I had the carburetor, alternator, propeller, fuel pump, and engine mount overhauled and had the full treatment for the baffles by Baffle Boy, and installed a new vacuum pump. The magnetos were an exception because they had only about 200 hours since new; Slick magnetos don't need to be taken apart until the 500-hour recommended service interval.

When it came time to add oil, I was faced with the mineral oil versus AD (ashless dispersant) oil debate. I've written about this before and have concluded that in terms of wear characteristics, there is no difference between straight mineral oil and AD oil, even the multiviscosity types. This doesn't apply to oil like Shell's 15W50, which has a partial-synthetic base. But I have in the past broken in plenty of engines and cylinders with straight-weight Aeroshell 50 AD oil with absolutely excellent break-in and oil consumption results.

However, as an airplane owner working with an overhauler, especially a persnickety one like Michael Peters at KTM Mid-Atlantic Engines, I have a constraint. Most overhaulers provide warranties and these depend on certain factors, one of which is the type of oil used for break-in. Lycoming still recommends the use of straight mineral oil for break-in on non turbocharged and certain other engines like those that use the automotive-style rocker arms. And Michael does prefer using mineral oil for break-in. So that's what I used, even though I don't think it makes any difference. As long as the mineral oil isn't left in too long, then there won't be a problem with sludge buildup, which is what the ashless dispersant package in AD oil is designed to eliminate.

There is another element to this story: how to ensure quality control when a mechanic is working alone. We all know that many mechanics work by themselves, but there is no formal quality control procedure for solitary maintenance. The FAA seems to be rather quiet on this subject. All of you who work for larger shops, mutlimechanic corporate flight departments, and airlines know that there is someone to back you up. And many operations have formal procedures for inspectors to check mechanics' work. But there are many one-man maintenance shops out there and one-mechanic corporate flight departments, and how do they ensure quality?

For my part, I try to create a work card, which is basically a checklist, for each operation. For the engine installation, I used the checklist for the annual inspection, and I went over it twice. The first time, I found two important items that I had done incorrectly; a badly positioned magneto holddown bracket on the right magneto and hooking up the carb heat valve backwards. After fixing these items, I went over the checklist again to make sure I didn't miss anything.

After a fairly brief ground run--another Michael Peters recommendation--I took a final look over the entire engine, buttoned up the cowling, and went flying. The overhauled engine produced plenty of power for an hour's worth of zooming around over the airport at a high power setting.

After landing, I removed the cowls and was pleased to see not one drop of oil anywhere on the engine and very little oil burned during the flight. A check of torques on the engine fasteners after a few more flying hours found that everything was nice and snug, and oil leakage was still zero. Michael knows how to build a tight engine.

My partner and I have put more than120 hours on the engine since the overhaul, and it's running strong and burning very little oil for an O-235-C model. There were a couple of drops of oil around the oil pan gasket, but retorquing those fasteners seems to have taken care of that problem.

The final question: was overhauling the engine worthwhile, or should I have paid for a factory overhaul from Lycoming? In financial terms, it's a wash. You don't save a lot by overhauling your own engine. The labor part of the equation is a very small percentage of the total, and if you're going to buy new cylinders, you might as well go for the factory overhaul. Because I had a cracked crankshaft, it's possible that I saved some money by finding my own used crankshaft instead of having to get dinged by Lycoming for a bad core. But, in all my past dealings with Lycoming factory engines, I've never had to pay for a bad core, so I'm not sure how that would have worked out.

The big benefit was that I got to spend time with Michael Peters, a fantastic engine man and a teller of great stories, and see how techniques learned over years of putting engines together can make an overhauled engine feel that much better when I'm the one flying behind those furiously pounding pistons.
-- By Matt Thurber

VENDOR LISTING

(note: the author paid for all materials and services used for this engine overhaul)

Aero Accessories
(fuel pump, vacuum pump)
Phone: 336-449-5054
Web: www.aeroaccessories.com

Aero-Care/Baffle Boy
(baffle repairs)
Phone: 978-544-9005
Web: www.aerokare.com

Aircraft Specialties Service
(engine component inspection,repair)
Phone: 918-836-6872
Web: www.aircraft-specialties.com

Divco
(crankcase inspection/repair)
Phone: 918-836-9101
Web: www.divcoinc.com

Kosola & Associates
(engine mount repair and overhaul)
Phone: 229-435-4119
Web: www.kosola.com

KTM Mid-Atlantic Engines
(engine overhaul)
Phone: 301-228-3884

LORD
(engine mounts)
Phone: 800-458-0456
www.lord.com

Modified Aircraft Accessories
(alternator overhaul)
Phone: 502-957-6312

New England Propeller Service
Phone: 860-873-1494
Web: www.neprop.com

Precision Air
(carburetor overhaul)
Phone: 305-594-9662
Web: www.precair.com

Rick Romans
(engine component inspection, repair)
Phone: 918-835-1311

Superior Air Parts
(misc. engine parts)
Phone: 972-829-4600
Web: www.superiorairparts.com

Textron Lycoming
(new cylinders, misc.engine parts)
Phone: 570-323-6181
Web: www.lycoming.textron.com