Here as a basic briefing on Corvair flight engines for builders getting a first look at using one.
Above, A 3,000 cc Corvair flight engine. I built this particular one in 2012 for the SPA Panther aerobatic aircraft prototype. The Corvair is a popular option on more than 20 different experimental airframes.
The Corvair is a General Motors designed engine, manufactured by Chevrolet. 1.8 million engines were built in the Tonawanda New York engine plant between 1960 and 1969. The Corvair has been flying on experimental aircraft since 1960, and I have been working with them as flight engines since 1989. It is a story of careful development and testing, a slow evolution to the engines we have today. It is ‘old and proven’ rather than ‘new and exciting.’
Configuration: The engine is a horizontally opposed, air-cooled, six cylinder configuration. We only promote its use as a simple, direct drive power plant. The engine configuration is very similar to Lycomings and Continentals.
Displacement: The engine is effective without a gearbox or belt drive because it has a comparatively large displacement. Between myself and SPA, we have versions that are 2,700, 2,775, 2,850, 3,000 and 3,300 cc. The smallest of these has twice the displacement of a Rotax 912.
Power: Corvairs have several different power ratings. 100, 105, 110, 120 and 125+hp. These correspond to the five displacements listed above. They make their rated power at 3,150 rpm. They have wide power bands, making 75% power at 2,650 rpm. All engines will exceed their rated power at higher rpm, and they can be continuously run at full power at 3,400 rpm without damage.
Weight: The engine weighs 225-235 pounds ready to run. This is effectively the same as a Viking 130 and slightly less than a Continental O-200. It’s installed weight is 35 pounds more than a 912 Rotax, 25 pounds more than a Jabaru 3300. The Corvair is 40 pounds lighter than a Lycoming O-235. Larger Corvairs are slightly lighter because they have special cylinders made for them which make these engine lighter.
Reliability: From the factory, the Corvair made up to 180 HP in the car and turned more than 5,500 rpm. The engine is reliable and long-lasting because we are only operating at 60% of these levels. Conversion engines that run at the car’s red line rpm historically have short lives and cooling issues.
Cost: We sell complete engines from $12,750 to $17,750. However, 90% of our builders assemble their own engines working from our Conversion manual, DVDs, parts and support and a rebuildable core engine they pick up locally. Typically, they budget $8,500-10,500 to build a first class, zero timed, engine. Budget motors can be built for as little as $6,500.
Cooling: The Corvair has a factory cylinder head temp limit of 575F. This is the highest limit on any mass-produced air-cooled engine ever built. The engine as also the first mass-produced turbocharged car. GM engineered the motor to have excellent heat tolerance and heat dissipation. In aircraft the engine typically runs at 325 to 350 CHT.
Parts availability: Every wearing part in the engine has continuously been in production for 5 decades. The engine pictured above, only has an original pair of cases, and oil housing and cylinder head castings. All other parts in the engine, including the crankshaft, are brand new. Many of the parts in the engine, like the lifters and valve train, are common to Chevy v-8s. There is no part availability issue.
Ignition: The fleet of flying Corvairs is about 500 aircraft. More than 90% of them have a dual ignition system that I have built. Our system uses two redundant systems, one points based, the other a digital electronic system. The design has two of every part potentially subject to failure, but it utilizes one plug per cylinder. Six cylinder engines can fly on one cold cylinder, most 4 cylinder engines can not. We have dyne proven that a Corvair running on 5 cylinders will still make 78-80% power. Plug fouling is unknown in Corvairs because the ignition system is 40,000 volts and uses a plug gap twice as wide as a magneto system.
Fuel: The Corvair can use either 100LL or automotive fuel. It is not bothered by ethanol in the fuel.When Corvairs were designed, car gas was a lot like 100LL; for the last 35 years every mile driven by Corvair cars was done on unleaded car gas. Many engines like 912s and modern car engines do not have exhaust valves that can withstand the corrosive nature of 100LL. We use stainless and Inconel valves in Corvairs with rotators on the exhausts.
Maintenance: The Covair is low maintenance. The heads never need retorquing. The valves have hydraulic lifters and never need to be reset or adjusted. I dislike the term “maintenance free”, because it implies a “no user serviceable parts inside” disposable appliance mentality, but the Corvair is a solid, robust, machine which holds its adjustments, but our program is aimed at teaching builders to be self-reliant owners.
Goals: If one of your goals is to be the master of your engine and airframe, the Corvair is an excellent choice. There are many engine options for people who just want to buy something. Our efforts are aimed at expanding the personal knowledge and skills of each builder.
Made in the USA: In an era where everything seems imported and companies like Continental have been sold to the Chinese Government, We have kept the “Made in the USA” option for builders who prefer to employ fellow Americans. Virtually every part in the engine, with small exceptions like the distributor cap (made in Mexico), are made by American craftsmen. Because we also sell engines outside the US, we are a Net Exporter, helping correct the trade imbalance.
Corvairs have proven themselves to serve a very broad variety of builders. Many alternative engine options are offered only as a complete import, more of an appliance than a machine, with little or no consideration of the builders, skills goals, needs, budget or time line. The Corvair has options to address these valid considerations, because your power plant should conform to you, not the other way around.
This said, Corvairs are not for everyone. In the 31 years I have been in the EAA and working with builders, the Corvair has always been very popular with ‘traditional homebuilders’, the people who have come to experimental aviation to discover how much they can learn, understand and master. The expansion of the EAA has brought more of these builders, but it has also brought a great wave of people, incapable of distinguishing between mastery of an aircraft or an engine and just merely being its buyer and owner. People who’s consumer mentality and short attention spans are better suited to toy ownership than mastery of skills and tools in aviation. Corvairs, and perhaps experimental aviation, are a poor match for such people. Many salesmen in our field will gladly sell anything to anyone with green money. I am an aviator, not a salesman, and the gravity of the subject requires more frank discussion and ethics than many salesmen bring to the table.
If you came to experimental aviation to find out how much you can master, not how little, then you are among the aviators who follow Lindbergh’s timeless 1927 quote: “Science, freedom, beauty, adventure: what more could you ask of life? Aviation combined all the elements I loved.” Even if you are brand new to aviation, I am glad to work with you. I have a long history of working with builders of all skill levels. We have a number of successful builders out flying who are the masters of both their airframes and engines, who had never changed the oil in a car before building their plane. If you got into experimental aviation just to buy stuff, then any salesman will do just fine for you. If you got into experimental aviation to learn, develop your own skills and craftsmanship and make things with your own hands, then who you work with really matters. You can’t become and old school homebuilder / motor head by buying things from salesmen. They have nothing to teach you. What you will do in experimental aviation is not limited by what you already know. It is only limited by what you are willing to learn, and selecting experienced people to learn from. If you are here to learn, I am here to teach. It is that simple.