What's a core?

[Robert M]

Could someone explain to me what is meant when an engine is refered to as a "core"?

[pierre smith]

Hi Robert,
When an engine is 'runout', and accessories have been removed, what remains is referred to as a core. A good example of this is a four cylinder Lyc. The factory calls them 2000 hour engines by suggesting that they should run 2000 hours with normal use and regular oil changes. It is not mandatory to overhaul an engine when it reaches the manufacturers suggested TBO as long as oil consumption and compressions are acceptable.(Many Lycs have run 2700 and some over 3000 hours) When it finally loses compression and/or starts using a lot of oil, then it's time for overhaul. It is then a 'core', with no mags, alternator, carburetor or vacuum pump, and has a preset value if you trade it to the factory or a remanufacturer for either a reman or new engine,
Regards,

[rgbewley]

Sure. When engine builders talk about a core they mean a used engine that is either "run out" (at or past TBO), had a prop strike or removed from an airframe for some other reason (like an engine upgrade.) This core would be the whole engine (crank, cases, cam, rods, gears, etc.) Sometimes cores do not have some accessories like magnetos.

What type of core to buy? Look for a first run TBO engine where the aircraft owner has removed the engine for a reason other than damage as a first choice. These are more and more difficult to find because the experimental market has absorbed so many cores and expensive for the same reason. Plus, most people who put in a new engine trade their core in for some type of credit. So, most cores are found at salvage yards and come from damaged airplanes (some severe, while some have minor engine damage but the airframes were destroyed.) Make sure that your core is complete and that whomever you buy it from will ensure that the crank and cases will repair. I would not recommend buying a core that had been submerged. It is also beneficial to have the log books and the data plate from the engine to help you know the engine's history. Most salvage yards buy engines from Europe and tell you that they don't have log books.

Another thought, depending on your engine model, Lycoming and the PMA manufacturers have experimental engines that are available new which can actually cost you less than buying a core and having an engine shop overhaul it to new limits for you. The p/h IO-360 for example.

Hope this is helpful to you. Good luck.

Rhonda Barrett-Bewley
Barrett Precision Engines, Inc.
2870-B N. Sheridan Rd.
Tulsa, OK 74115
(918) 835-1089 phone
(918) 835-1754 fax
www.barrettprecisionengines.com

[gmcjetpilot]

Also used in terms of a trade in. Many parts say at your auto store require a CORE to exchange for a rebuilt carburetor, alternator, starter or water pump. Same with an engine. Most of the time you don't get the core back, you receive another unit rebuilt. For aircraft engines it is basically a usable engine that can be rebuilt. There is an expectation that major parts of the engine can be reconditioned and reused.

Keep in mind if you by an engine as a core for trade in for a rebuilt they will charge you for any parts that are not servicable or usable. A bad crank, case or cam could ruin you budget. Items usually rebuilt or refurbished are the case halves, rods, crankshaft, cam, lifters, gears and many times cylinder to name a few. Items like nuts, bolts, pistons, rings, bearings, valves and guides are replaced with new. Lycoming has a service letter describing a complete list of parts that should be replaced in an overhaul.

Most important do NOT pay to much for a core, even if it has 100% serviceable parts. A rebuild can easily cost up wards of $9,000-$12,000, more if any major component is not usable. A replacement of the crank for example is roughly $4,000. If you pay too much for a core and have to replace any major component, you might as well have bought a new engine for appox $20,000. It would be cheaper. Most cores are going for about $3,000-$6,000. Sometimes they are sold as running engines with usable time left. If the engine is sitting on the floor in the corner of a hanger it's hard to know if it's usable. Last advice. If the "CORE" does not come with excellent records, log books, the core is not worth much. You have to verify what kind of condition the engine is in. If it is not currently in a plane and running that is hard to do. This is where good records are so important. BUYER BEWARE! Most companies want TOO much for their JUNK. Usually the best cores come from a senerio like another RV builder is upgrading to a larger engine and sells their existing engine.