Premium overhauls

Premium Overhauls "New Limits" is the only way to go By Greg Napert October 1998 Today's reciprocating engine overhaul market is very competitive. With a wide variety of small shops offering a large variety of overhaul services, and...

Premium Overhauls

"New Limits" is the only way to go

By Greg Napert

October 1998

Today's reciprocating engine overhaul market is very competitive. With a wide variety of small shops offering a large variety of overhaul services, and the engine manufacturers themselves providing overhaul capabilities, it has become harder than ever to continue to provide high quality overhauls at competitive prices.

One facility that has chosen to continue to offer premium overhauls, despite these conditions, is an overhaul facility called Penn Yan Aero, located in Penn Yan, NY.


A modestly appointed, yet fully-equipped and highly organized shop, nestled in the heart of New York state's Finger Lakes, the company has been overhauling recip engines for over 50 years. Daryl Middlebrook, owner and president of Penn Yan Aero, began the operation in 1964 when he was working for his dad in the FBO operation and saw an opportunity to concentrate on overhauling engines. He invested in the tooling he needed and registered the repair station with the FAA. Since that time, Penn Yan has abandoned the FBO business and has focused solely on the overhaul business — going from overhauling six engines per year in 1964 to five engines per week in 1998. The company's focus on engine overhaul has become so strong, it no longer does installations or removals — even though it operates out of a hangar at the airport. The hangar has been completely converted to an overhaul shop and warehouse and all engines are received via land conveyance.

Penn Yan overhauls both Continental and Lycoming engines as well as repairing prop strikes, sudden stoppages, metal contamination, etc. It also supplies STCs for horsepower upgrades for various engine and aircraft installations.

There are many different types of overhaul shops in the industry. The regulations, which govern overhauls are broad enough that they allow overhaulers to do a wide variety of maintenance on a particular engine and still call it overhauled. Some shops inspect an engine and reassemble it with serviceable parts. And at the other end of the scale are shops that return the engine to "like new" tolerances with new and repaired components.

Middlebrook says that Penn Yan likes to consider itself a "premium" overhaul facility and doesn't offer anything but a "new limits" overhaul. "There are plenty of people out there selling Volkswagens and such but we want to be known as a premium overhauler that sells a quality product," he says.

Although some of the extra steps that Penn Yan takes to ensure a quality product are considered by some to be what some refer to as "blueprinting," Middlebrook says that he doesn't like that term as there is really no definition for it. Instead, he likes to think of Penn Yan as doing whatever it takes to provide the best quality of overhaul possible.

Improving on the basics
Middlebrook explains, "One of the biggest things that you can do to improve the performance of any horizontally opposed, carbureted, or fuel injected engine is to equalize fuel distribution. You will find that certain engines distribute fuel very evenly, and some other engines are poor at doing that. Also, the aircraft that the engine is installed in makes a lot of difference, even with the same engine.

"So, we spend a great deal of time porting and polishing our cylinder heads. We are very careful to dimension our ports to the same size and remove any slag or inconsistencies in the casting." He explains that a large amount of porting and polishing experience that they have gained over the years is out of necessity as they weld cracked heads. Porting and polishing is a critical step that is needed to return the head to its original condition after a welding operation.

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