I really enjoy engine overhauls. I’ve been working on engines for over 45 years so I know just a few things. You can bring me your airplane or just the engine. I’ll fix just the way you want it, from a basic “new bearings, rings and seals” freshen-up repair, to a full-blown “make everything new with a fancy paint job” overhaul. Whatever you want.
Important Legal Definitions:
New: This is a new engine with all new parts. Obviously, I can’t build you one of these.
Rebuilt: This is an engine that has been torn down, inspected and reassembled with new or used parts that meet new part specifications. This is the so-called “zero-time” engine. The parts aren’t really zero-time; they might have thousands of hours on them but nobody really knows because the logbooks are thrown away. But so as long as they meet new part specs, they are called declared “zero-time” and a new logbook is started. The only people that can do this work is the factory or any factory-approved shop. For the big Continentals, I think there is one shop authorized to do this. Obviously, I can’t do this either.
Overhauled: This is an engine that been torn down, inspected and reassembled with new or used parts that meet serviceable specifications. Now, obviously there is nothing to stop me from overhauling your engine with new parts, and making it just as good as a factory rebuilt engine. Except that you know exactly how many hours are on all of the parts. Or we can save some money and use your old parts, as long as they meet serviceable limits as posted in the engine service manual. Doesn’t that sound better than getting an engine with parts that have an unknown number of hours?
Reman: Legally, there is no such thing as a Remanufactured engine. That word has absolutely no meaning to the FAA. Some shops use the term because it rolls off the tongue so easily, but be aware that, legally, it means nothing.
IRAN: Not legally defined by the FAA but generally accepted to mean Inspect and Repair As Needed.
So what happens when your engine gets an IRAN? Well, the engine is disassembled, cleaned, and all the parts are inspected. Then the engine is reassembled with only the parts that are needed… parts that don’t meet service limits. You might have old engine that runs just fine but it leaks oil everywhere, burns more oil than you would like and the oil pressure is right at the bottom of the green. So… replace the crank bearings, hone the cylinders, replace the rings and give the cylinders a valve job. The camshaft and lifters look just fine? Reinstall it. The oil pump looks fine? Reinstall it…
Example: one of the parts that must be replaced in order to call it an overhaul is the big gear on the rear of the camshaft. Problem is, the last time I checked it was $6000. And they never break. So reinstall it and you can save a LOT of money by just repairing the engine instead of overhauling it. Remember that Continental publishes service limits for almost every part in the engine. So if you’re trying to save money and the parts are within limits, reinstall them.
Is an overhaul with all new parts better than an IRAN? Absolutely. But let’s face it, not everybody can afford the $60,000 (in 2025) price tag of a “new-limits” overhaul. And some of us are getting up in years and we realize that realistically, we’re only going to put another 200-300 hours on our plane before our bodies “time out.” So why pay for an engine capable of going another 1500 hours? Just something to think about…
Now, here are some terms that just annoy me…
Top Overhaul: You see this term a lot. Somebody replaces all of the cylinders and calls it a “Top Overhaul.” Except there is no such thing. The FAA does not recognize this term. Even if someone replaced all the cylinders with new, it’s still just a “Repair.”
Major Overhaul: Another term that the FAA doesn’t recognize. I assume when someone uses this term, they mean “Overhaul.” But since there is no such thing as a Minor Overhaul, what is the significance of calling an engine overhaul a Major Overhaul? It sounds nice, but it doesn’t mean anything.