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Rebuilt Engines?
Thinking of purchasing an "experimental" rebuilt engine to save money?

Think Again!

As the experimental aircraft market grows, so does the demand for engines to power these new aircraft. Experimental aircraft may be powered by a certified engine or a non-certified engine. The non-certified "experimental" engines are usually an auto-converted engine, or an engine that was previously certified. However, after a certified engine is "rebuilt", it may not conform to the original type certificate due to installation of non-approved parts or modified parts, or may be rebuilt by a non-licensed mechanic. Therefore, these type of rebuilds are strictly for experimental use.

The focus of this report is on the non-certified or "experimental" rebuilt engines. There are several companies that specialize in rebuilding engines for experimental use. Some of these companies have an outstanding reputation of providing a good product and standing behind their workmanship.

Unfortunately, there are some companies that sell "experimental" rebuilt engines in which they neither provide a good product nor stand behind their workmanship. These companies can potentially give the aviation industry and the aircraft engine manufacturers a bad reputation.

Recently, a "0" SMOH "experimental" rebuilt Franklin 6A-350 (220 HP) engine was disassembled and inspected due to problems discovered by the airplane owner during engine ground runs. This "rebuilt" engine was sold to the airplane owner from a company that claims to specialize in rebuilding aircraft engines for "experimental" use.

Some of the findings of this rebuilt engine would indicate the rebuilder knew what he could get away with by selling an engine for "experimental" use. One must remember the FAA has no control or authority over aircraft engines deemed for "experimental' use. The old saying "caveat emptor" or buyer beware is the motto of the FAA when it comes to purchasing "experimental" aircraft engines.

Below is a summary of the inspection report on this "experimental" rebuilt engine sold as "0" SMOH and only had a few ground runs on it!

Cylinders:

All six cylinders were cracked. One of the cylinders was so severe that the crack went from the intake port, down through the intake seat and around to the spark plug hole. A serious safety issue! Some cylinders were welded on the outside of the intake port to mimic the "heavy" cylinder design. The cylinders were assembled with used valves and used valve springs. No indication the valve guides were replaced.

The plain washers that were installed between the cylinder base and the cylinder hold down nuts were too large to seat in the counterbore. This could result in improper torque of the cylinders to the crankcase and possible cylinder separation from the crankcase.

Pistons/Piston Rings:

Used pistons and piston rings were installed. The pistons showed severe wear. It is evident that the pistons and piston rings were cleaned through a bead blasting process.

Camshaft/Lifters/Pushrods:

A few of the camshaft lobes were welded up and reprofiled. (The process of welding up camshaft lobes is not approved by the engine manufacturer nor the FAA.) The outside diameter and the face of the lifter bodies were severely pitted. It appears an attempt was made to reface the lifter bodies, but pitting on the face of the lifters was not totally removed. The pushrods were severely pitted and is apparent the pushrods were bead blasted to remove the rust.

Fuel Pump:

A non-certified fuel pump was installed on the engine. The oil seal was incorrectly installed.

Connecting Rods:

The connecting rods installed on the engine are for a 165 horsepower engine, not the correct connecting rods for a 220 horsepower engine.

Crankcase:

The crankcase had several cracks in the webbing. It was determined that the crankcase is not repairable.

Crankshaft:

The crankshaft gear nut that holds the damper to the crankshaft was not torqued to proper specifications and the bend tab was not peened over to prevent the nut from backing off. The crankshaft main and rod journals were under minimum standard limits and pitting was discovered on the rod and main journals. An incorrect crankshaft seal was installed which was designed for a different engine make.

Carburetor:

The carburetor showed no signs of being rebuilt. Upon inspection, the carburetor still had the outdated composite float installed which was not in compliance with carburetor manufacturers Madatory Service Bulletin dated 10-15-90.

After reviewing the list of problems found on this "experimental" rebuilt engine, one would ask is it worth saving a few thousand dollars and ending up with an unsafe aircraft engine like this? Better yet, why would someone sell an unsafe product like this? As we stated in the beginning, the experimental aircraft market is growing every year; therefore, new airplane builders and airplane owners are entering the market. The new airplane owner may not have a complete understanding about some particular products and rely upon good faith that the supplier will provide them a quality product since it is for aviation use. This assumption can lead to a costly education and possibly disastrous results. As one of our customers said, "Buying an experimental rebuilt engine is like buying a parachute with holes in it."

Caveat Emptor!