William Wynne

The Corvair Authority
5000-18 HWY 17 #247
Orange Park, FL 32003


Maximum Horsepower

Every day I answer the question: "What is the maximum amount of reliable horsepower I can get from a Corvair motor?" My extensive testing over the years indicates it is 100-120hp with the degree of reliability necessary for flight engines.

It has been said that you can have your choice of two when it comes to inexpensive, reliable and extremely powerful. This holds true for the Corvair motor. The motor is an inexpensive alternative engine in the range of 100 to 120hp. I am currently working on turbo systems to slightly boost the power beyond this. If you attempt to increase the horsepower significantly beyond this, it requires extensive and expensive modifications to achieve higher horsepower. Beyond gearing, the motor could be heavily turboed, but would require extensive internal modifications such as driven in through studs, roller valve train, digital ignition, etc. All of these things are expensive and unproven. By the time you paid for them, you could have purchased the equivalent amount of Lycoming horsepower for less money ... but you would not have the proven reliability of Lycomings.

Does this mean the Corvair's not a great engine? Of course not! It just means that the vast majority of people will be most happy utilizing it as a replacement for an O-200, and in some instances, an O-235. But the engine in its inexpensive, simple form, will never do the work of an O-320.

Even though some people will read the above words as a challenge, and point out that the factory rated the motor to 180hp in the car, I simply state that my years of experience indicate that this cannot be done cost effectively in an aircraft situation. For the builders looking for motors producing 160-180hp, it is my firm belief that Lycoming 320s and 360s cannot be challenged as the most economical and reliable power plants. I feel these builders would best be served by my honest answer that the Corvair motor is not the motor for them.

Off the top of my head, here's a partial list of the airplanes that I know have successfully flown on Corvair motors: J3 Cub, Pietenpol Air Camper, Pietenpol Sky Scout, Breezy, Tailwind, KR2, VP2, Sonerai II, Volmer Sportsman, Christavia Mark I, Boredom Fighter, Fisher Horizon, Corben Junior Ace, Nieuport 12, Skycoupe, Sonex, Benson Gyrocopter and Davis DA2. In addition to these, there's been a handful of one-off designs. There have been a lot of other projects that I've only received partial information on. You can watch the list grow longer at the Flying Planes page.

Notice that virtually every one of these aircraft was designed for a VW motor or a 65-100hp Continental. Nowhere among the list is an aircraft originally intended to be powered with 160hp. Builders considering a project for their Corvair motor should recognize this.

In the coming months and years, out of builders' workshops will come inexpensive, successful Corvair conversions powering other designs such as Zenair 601s, Europas, Buttercups and others. We may even see a number of twins, eventually. There are a number of great designs in this horsepower class well within the capabilities of an inexpensive Corvair motor converted in a homebuilder's shop. With some dedication and effort, your aircraft will one day rank among these successful aircraft.

Corvair Engines and the Sonex

Updated November 27, 2004

Friends,

We are putting this on our Web site as an extremely frank discussion of the concept of installing a Corvair engine in the Sonex airframe. We have previously posted brief discussions discouraging the combination. As time went by, I found that it was necessary to expand with more technical reasons why I felt that it was a poor combination. Here is the latest update on my evaluation of the combination. In a nutshell, my opinion has not changed. Out of respect for the readers who are thinking people, who are not inclined to take "it's a poor combination" as a complete technical discussion, we're expanding this section of the Web site. I ask that you read it carefully, and consider it in its entirety. It is a plain discussion. There are no hidden points or agendas, and there's nothing to be read between the lines.

John Monnett, the designer of the Sonex, has stated that the firewall forward max weight for the aircraft is 200 lbs. A handful of Corvair engines have been built slightly below this weight. It takes a special effort to lower a Corvair engine below 200 lbs. and would not include electric start, etc. When the weight of a motor mount, cowling, prop, exhaust, etc., is considered, it is simply not possible to build a Corvair engine package for the Sonex which will meet the designer's requirement of 200 lbs. or less total firewall forward weight. This is the beginning of why the Corvair is not a good match for the Sonex airframe. Initially, it was the only aspect on which I chose to elaborate.

About a year and a half ago, the first Corvair powered Sonex airframe began its test flights. It belongs to Del Magsam of Wisconsin. To date, this remains the only Sonex airframe to be powered by a Corvair engine. Del is a customer of ours, but was on his own to work through the difficult process of fitting the Corvair engine to the airframe. Out of respect for his accomplishment, as we would for any of our other customers, we wrote a story about his airplane in our own newsletter, The Corvair Flyer. I did not then, and still do not now, consider this acknowledgement as endorsing or promoting the combination. Over the years, we've done a lot of work to develop firewall forward components to install Corvairs on various airframes, and people who follow my work will clearly see that I haven't developed or endorsed a single component specific to the Sonex airframes.

The reason for this is simple: I know the Monnetts fairly well, and they have presented a number of good technical reasons why it's not a good match. Let me be clear and say that no one from the Monnett family has ever asked me to put any of this on our Web site. It's just easier for us to have it here and avoid repeatedly answering the question individually as private e-mails come in. Below, you will read several more reasons why people who are thinking about the combination may want to reconsider. These points are my own, and are not the opinion of the Monnett family or Sonex Ltd. If you have further questions or issues with these points, it would be properly directed to me and not the Monnetts.

Although I did not follow the progress of it closely, the discussion of non-approved engines in the Sonex airframe (approved engines are the Jabiru 3300 and 2200, and the Aerovee 2180) has occasionally become very heated. I have not taken part in this, and have done nothing to fuel it. Keep this track record in mind when you read my thoughts here. If anybody thinks of taking something I've written here and using it as ammunition in an Internet squabble, you've completely missed my tone and intent.

The official position of Sonex Ltd. is that only airplanes that have one of the three factory approved engines are really Sonexes. While this may seem like a small point, in many ways it isn't. I understand their position entirely, and it's not a new position in this industry. People who have been around sport aviation for a while will remember that Burt Rutan was adamant and very vocal about people using unapproved engines in VariEzes and LongEzes. He felt that he had designed a complete airplane with careful consideration given to the powerplant. The record showed that airplanes built to his plans had a vastly superior track record over those which had been modified. He did not want the blame for work which was not in the plans, nor did he want unapproved installations polluting his insurance statistics. While a handful of people thought if they'd purchased plans from the Rutans that they had a right to name anything they finished a VariEze or LongEze, most reasonable people saw Burt's position. Likewise today, I think that most reasonable people understand Sonex Ltd.'s position about the name of the aircraft. Thus, if you plan on putting a Corvair engine on the front end of a Sonex, it's no longer going to be a Sonex.

First, this means that you may have a very difficult time getting it insured for a reasonable price. This especially applies to hull insurance. I've dealt extensively with the EAA's insurance provider to obtain reasonably priced coverage for Corvair engines in 601 airframes. When you install an unapproved engine in an airframe that can no longer be grouped with its original brethren, you're now in an insurance group of one. Furthermore, it will have a big effect on resale value on the plane should you choose to sell it. To aid in the discussion, please take a look at the following photographs. Keep in mind as you look, they're merely an acknowlegdement that some people are trying the combination, along with a frank discussion about it. If we chose not to put the photos on the Web site, a reader might falsely assume that someone had solved all the issues and I was unaware of it. I keep close tabs on most things going on in the world of Corvairs, and I present this to illustrate that we're aware of it and even this aircraft, which has not flown, does not address the installation issues to the satisfaction of Sonex Ltd.

Most people looking at the above photo would say it's a William Wynne 601 Nosebowl on a Sonex, probably with a Corvair engine in it. Considering the above paragraphs, anybody who said this would be off the mark. This is a plans built airplane. Obviously the builder started off with a set of Sonex plans. But because he finished off with a Corvair engine, the plane is realistically no longer a Sonex. The builder of this aircraft refers to it by the name of "Cleanex" because he understands the logic of Sonex Ltd. I additionally want to point out that the nosebowl on this aircraft started off life as a 601 Nosebowl, but underwent some serious surgery to fit this airframe. We didn't do it. The builder did. Nor do I have any intention of re-creating our 601 Nosebowl to fit the Sonex. Should anyone see this airplane in the future, it would be most accurate to refer to it as The Cleanex, and understand that it does not actually have a 601 Nosebowl on it.

Here's a photo of the Cleanex and its builder in front of my hangar. A few people who saw this photo made jokes about the "Builder Protection Program" with a nod toward John Monnett's reportedly sharp temper. In reality, the Monnetts probably know who this builder is. The reason he chose to wear the paper bag is to avoid answering any questions about his plane, or being drawn into any type of Internet controversy surrounding his choice of engine. The decision was his, and he does not want anyone to feel that his choice should legitimize theirs or encourage others. Although he's wearing one of our shirts, I can assure everyone he's not a member of my staff, and before you take the trouble of e-mailing me, let me assure you I will respect his wishes and won't divulge his identity.

The engine in the Cleanex is a highly modified Corvair powerplant. This particular installation is a hybrid engine utilizing VW cylinders machined to fit the Corvair case. While standard Corvair engines can be built from our Conversion Manual for approximately $3,000 to $3,500 in parts, this is no standard conversion of a Corvair. The builder intended to lower the weight as much as reasonably possible, and increase the horsepower to get as close as possible to the Jabiru 3300's output. This conversion cost about $7,500 in parts, and the builder had to take a lot of time to assemble it. High end engines like this, with hybrid VW cylinders, are more expensive and far more difficult to assemble correctly than our standard 100hp model, straight Corvair conversions. My Manual discusses both engines, but it's important for people to note that standard Corvair engines will not come even close to meeting the Monnett's weight restriction firewall forward. This engine weighs approximately 8 pounds less than a standard Corvair, but it's still not going to meet the 200 pound limit. When this airplane is done, the builder has offered to weigh it in public to demonstrate the reality of the combination. It has been falsely reported many times that there is some modification that can be done to the Corvair to meet Sonex Ltd.'s weight restriction.

Here's a view of the underside of the Cleanex's motor mount. The Corvair uses a bed mount. The approved engines for a Sonex all use a Lycoming-style mount. This is another factor in why the firewall forward weight with a Corvair would be outside the limits. Bed style mounts on reverse sloped firewalls are going to be inherently heavier. Del's engine installation made adapters to mate the Corvair to a standard Sonex mount. I did not like the way that turned out. It functioned, but I felt it overstressed the Sonex mount. Additionally, it precluded the use of our ignition system, which I feel is the most proven and reliable ignition system for Corvairs. The Cleanex has one of my ignition systems installed, and I like the layout of this motor mount far more. But keep in mind that this is far from an engineering evaluation. This mount was eyeball engineered. I did not build it. There were no stress calculations done. Nor was it load tested. Pete Buck did the structural analysis on the Sonex. He's one of the best engineers who ever made a contribution to sport aviation. It's a stretch to propose that an eyeball engineered motor mount would be the perfect complement to his airframe work. The Cleanex builder has no jig or plans for his mount. I did not put a tape measure on it, and I'm not in a position to comment on its design. If you choose to go with a Corvair powerplant in this airframe, this is one of the issues you're going to have to tackle.

This top view of the engine shows that the Cleanex builder chose to use a number of the products that we sell to put Corvair engines in other airframes. In the foreground is our Front Starter arrangement. This allows the use of a stock oil system. The Distributor shown is one of our dual ignition units. The cylinder head intake logs are left intact, but modified with our weld on intake pipe conversion. The point I'd like to make here is that this builder has chosen a difficult installation. To have the greatest degree of success, however, he has chosen to utilize as many proven components as possible from our inventory of parts. I do not promote the combination, however the reality is I would greatly prefer that anyone who is determined enough to build their own airplane like the Cleanex at least utilize the R&D work we have put into the Corvair to their full advantage.

The above paragraph may sound like doublespeak, but it's not. The reality is I recognize some people will do this. I don't want anybody feeling that they are an outsider and cannot utilize our basic R&D if they're going to attempt such an installation. Sonex Ltd. has never asked me if we have any customers in common. I feel their major issue is with people who want to call their done project a Corvair-powered Sonex or with people who would falsely argue the Corvair meets their specifications. I think most reasonable people would understand my position of not promoting the combination, respecting the Monnetts' wishes, but not isolating any Corvair builder in need of basic information. This simultaneously allows me to respect the wishes of my friends, and lower the risk of people attempting this type of combination.

Everything above can be considered a complete statement on the combination. For a very detailed look at how well I understand these issues, please continue to read down and consider the false claim that the cylinder heads on a Corvair can be significantly lightened. The engine shown in the above photos weighs slightly under 220 pounds installed. This excludes the mount. Someone might later try to claim they could further reduce the weight on the engine, but I doubt even a few pounds could be removed. Even a switch to aluminum cylinders, a topic which has been discussed but never installed on a running Corvair engine, far less a flying one, would not reduce the weight of the engine below 210 lbs. Any other starter arrangement will require modifying the oil system, which will increase the overall installed weight and reduce the reliability.

Cylinder Head Weight

I have a lot of data that shows the Corvair has an installed flying weight of about 225-230 lbs. This weight includes an 18 amp alternator and electric start. This is slightly below the installed weight of a typical O-200 Continental. Recently, several people have suggested that excess weight might be trimmed off the Corvair to allow it to meet the 200 pound weight limit of the Sonex aircraft. This is pure wishful thinking. Take a look at any picture of a Corvair engine we've built. Consider how big a 25 lb. steel barbell weight is, and then look at the motor and tell me where one of those has been left in place. 25 pounds of aluminum is roughly double that volume. The Corvair is a great engine, but it's not going to be a sub-200 pound engine with all of its accessories. Bare, stripped motors might approach this, but it is my strongest opinion that people would find a Corvair engine with its six cylinders on a short aircraft like a Sonex a very difficult combination to hand prop. To simply address the issue of the weight of the cylinder heads, follow the photos and descriptions below.

I recently heard the false claim that 5.5 pounds can be removed from each cylinder head. This is false. I have approximately 100 Corvair cylinder heads in my shop at any time. We've constantly experimented with the engine, and we have a number of special heads laying around. A little known fact about Corvair heads is that the 1964 and '65 heads are roughly a pound lighter each than '66-'69 heads. The later heads have additional strengthening and webbing. In our application, the strength is not a crucial issue, and we use both models of heads to build engines. It's important in cylinder head comparisons not to compare a trimmed 1965 head to an untrimmed 1966 model. This would allow the false impression of a weight reduction. Although in these photos you'll see the stock GM intake log trimmed off, I in no way endorse this. If you look closely at the head, you'll see that GM very cleverly used this log to stiffen the top row of head bolts. With it removed, the clamping on the head gaskets will be adversely affected. Additionally, I have numerous tests to show that the GM heads have excellent mixture distribution, and few modified heads can match this. The best approach to a reliable, powerful cylinder head is to leave it stock, or weld on an aluminum pipe to the stock log as we did on our 601 engine.

In the photo above is the lightest cylinder head we have in our shop, at 17.9 pounds. This is not a typical Corvair head. It is about 8 ounces lighter than stock because it is bored out to accept 94mm cylinders. It also has been bored out to accept 1.5" exhaust (an experiment not recommended). It also has had the intake flange removed from the top of the intake log. Being a 1965 head, it is the lightest head with which to start. Looking at this, you can begin to understand why someone claiming to have a 15 pound head may be exaggerating.

Here above we have another head pulled out of the experimental parts bin. It is also modified with 1.5" exhausts, and gutted for 94mm cylinders. This is a 1966 head. The intake tubes welded on here are nowhere near as stiff as the stock log was. This head can be considered structurally flexible. This is not desirable in any world. Notably, this intake setup, for all the effort involved, did not have as good mixture distribution as a stock log.

After measuring about 20 bare heads, this 1964 cylinder head stripped of its valves, above, was the lightest head still in its stock form.

Here above is the heaviest bare head I had in the shop. It is a 1966 model. This photo and the one above illustrate the one pound differential between 1964-65 and 1966-69 heads.

Above is a 1966 cylinder head. Before jumping to conclusions, please note that this head has valves, springs and retainers in place. It does not directly compare to the above cylinder heads. These 1966 and later heads have more material underneath the head bolts. While this is not a crucial flight issue, GM thought it was an improvement. To understand how light the stock log is, compare this with the following photo.

Above is the exact same cylinder head with the entire intake log bandsawed off. Just so that you can see that it's the same head, go back to the previous photo and note the saw curf and duct tape holding on the log for the photo. This clearly demonstrates that the log weighs only 1.5 to 1.6 pounds, and you have to put something back in its place. Even if this something only weighed half a pound, you would have destroyed the structural integrity of the head, messed up the mixture distribution, and spent a lot of time. Your reward? One pound saved.

Here is the log sitting on the scale, above. If somebody tells you this weighs 5 pounds, use your common sense to realize that a volume of 5 pounds of aluminum is a lot larger than this.

In conclusion, let the above photos illustrate the depth of knowledge we have from years of testing Corvairs, and my adherence to the facts when it comes to teaching people about the engine. Over many years, I watched as competing Subaru conversion companies, under extreme market pressure, exaggerated the horsepower and minimized the weight of an EA-81. In the end, the public caught on, and never believed most claims about the engine, even legitimate ones. With the Corvair, the situation is entirely different. I am the only commercial provider of Corvair parts and information to the experimental aircraft world. I am absolutely adamant that no one exaggerate the power or minimize the weight of the Corvair. It is a great engine, and it's plenty powerful and fairly light. It can certainly stand on its own merits. Any attempt to stretch the truth only damages the long term credibility of the engine, and undermines my work to make the engine the affordable powerplant that so many people in aviation need in order to participate.


Corvair Engines in the Zenair 701

The Heintz family has told me directly that they do not want engines which weigh 200 lbs. or more in the 701. Despite the fact that their 701 brochures have pictures of engines like O-200s and EA-81s, which weigh more than a Corvair, they do not encourage installations like this. The Heintz family has a lot of photos of customer built airplanes on their Web site. They obviously don't endorse everything that's in these airplanes. I assume the airplanes are on the Zenith Web site as acknowledgement of builders' successful efforts to produce a flying airplane. We have a handful of customers working on putting a Corvair in a 701 airframe, but I have not seen any serious progress on it yet, and no one has flown the combination. For anyone who asks about reducing the weight of the Corvair below 200 pounds, I ask that you read the Sonex section above carefully.

When I speak to people in person about the 701, I find that a number of them are attracted to the highly efficient methodology the Heintzes have brought to building airplanes. These people often said that they chose the 701 because they'd occassionally be operating off grass strips and wanted an airplane that was a good slow flyer. When speaking to these people, I always encourage them to consider the 601. Having a built a 601, and studied the 701 closely, I think they could be built in a very similar amount of time. They both use the Heintzes' design and building philosophy of very simple, quick to build airplanes. For the type of grass field flying that most people are interested in, the 601 is a surprisingly good performer. One of the places we stopped with the 601 in the Summer of 2004 was the annual Pietenpol Gathering at Brodhead, Wisc. This beautiful airport features modest natural grass runways. The 601 had no trouble operating out of this airport at full gross weight. The XL's highly efficient wing, with generous span and area, got the airframe flying and off the soft, wet grass quickly. The XL model features normal size aircraft tires, which do not have a problem with grass strips. Once in flight, Gus demonstrated in the flyby that the 601XL with 15 degrees of flaps can fly slower than an average Pietenpol. Builders who witnessed this realized that the 601 covers a broad performance spectrum. People with the most extreme performance requirements will still need a 701, but most homebuilders, especially ones sold on Corvair power, should take a good look at the 601. Its 44 inch wide cabin and 135mph speed are serious factors that most builders can take advantage of on every flight, whereas few builders really need the 701's radical short field capability. In either case, you'll enjoy the advantages of the Heintz family's decades of experience in designing and manufacturing good, simple airplanes.

Corvair Engines in Vans Aircraft

Friends considering powerplants for RV series planes:

I have spent the past 10 years developing and flight testing Corvair engines. The overwhelming popularity of the RV aircraft and the emerging popularity of the Corvair often leads to the question: "Would a Corvair be a satisfactory powerplant in an RV?"

The plain and simple truth is NO. It has taken years of development to get the 164cid Corvair motor to economically produce 100hp with the reliability that is required from flight engines. While we now have a 120hp 190cid motor, it makes its power at an elevated rpm, 3,200rpm, and it cannot be considered a direct replacement for the O-235 in this application. The O-235 and O-290 make their power at several hundred rpm less. I believe the Corvair's thrust level to be below what would be satisfactory for the RV-9.

I have received reports of a geared, turboed Corvair installation in an RV-9, but I do not know if the aircraft has flown. The builder of the planetary gear set told me his cost was $2,500. The engine overhaul was perhaps $3,000 and the turbo system was certainly another $1,500. At this point, you've spent as much money as you would have on a mid-time 150 Lycoming.

While the Corvair has been geared and turboed to produce more power, this is done at expense which typically exceeds the cost of the equivalent Lycoming power with nowhere near the reliability Lycoming offers. Simple Corvairs have an excellent history that common sense tells you would be lost with a highly complex installation.

Only the single seat RV-3 in its most basic form would be a possible installation for a direct drive, simple Corvair.

In conclusion, the RV series of aircraft and the Corvair engine are great designs, just not for each other, with the possible exception of the RV-3. The other RVs are not designed to achieve their best performance on 164-190cid engines like the Corvair.

As a person who has done more work with the Corvair than any other living person, I suggest you consider my words carefully. Anyone who is trying to disagree doesn't have the experience I do or is trying to sell you something.

Thank you.
William

Corvair History

Dear Experimental Aircraft Builder,

Thank you for your interest in my Corvair Conversion Manual and components.

I feel that the direct drive Corvair engine is an excellent choice for VFR sport aviation aircraft requiring a 100hp to 125hp engine.

The Corvair engine is a 164 cubic inch (2,700cc), horizontally-opposed, six-cylinder, air-cooled power plant. General Motors produced 1.7 million Corvairs between 1960 and 1969. All of these high quality engines have hydraulic lifters, torsional vibration dampeners, full flow oil systems, spin on oil filters, and aluminum cases and cylinder heads.

Corvair engines have been powering experimental aircraft since 1960. Flying hundreds of hours, EAA members Bernie Pietenpol and Waldo Waterman demonstrated that the Corvair engine made an excellent aircraft power plant.

Today, the Corvair engine still represents an excellent choice for home builders. With my up-to-date research and current Conversion Manual (written in 1996 and updated in 1999 and 2002), the Corvair is an easy engine to adapt to aircraft use. I provide information, drawings and components for converting Corvair engines for aircraft use. Complete engines are available on a special order basis (see the Engine For Sale Page).

Please feel free to e-mail or call with any further questions you may have. Thank you for your interest concerning my products. For more information on the development of my Conversion Manual, please see my Technical Support Page. Please see my Online Catalog for more information on my products.

Sincerely,
William Wynne
EAA #331351


Direct Drive Corvair Engine
Spec Sheet

Engine Model

O-164

O-190

Number of CylindersSixSix
CoolingAirAir
Displacement164 cubic inches (2,700cc)190cid (3,100cc)
Bore3.43 in. (87mm)94mm
Stroke2.94 in. (75mm)75mm
Compression Ratio9:19:1
Oil Capacity4.5 - 7.0 quarts4.5 - 7.0 quarts
Weight Wet, Ready to Fly with Electric StartApproximately 220-225 lbs.Approximately 212-217 lbs.
LengthApprox. 28 in.Approx. 28 in.
Width28.5 in.28.5 in.

Performance

HP100@3,150 rpm120@3,200
HP (Continuous)90@3,000 rpm110@3,000
Torque160 ft./lbs. @2,800 rpm200 ft./lbs. @2,800
Fuel93 Octane Auto Gas or 100 LL93 Octane Auto Gas or 100 LL
Fuel Flow5.6 GPH @ 75%7.0 GPH @ 75%

Accessories

Oil CoolerStock Corvair-Block Mounted, Can Be Remoted
IgnitionDual Ignition, Single Plugs
GeneratorAlternator - 14 Amp std., Larger Available
StarterHand Prop or Electric Start; Electric Start adds 20 lbs.
Prop FlangeSAE #1
Prop RotationLeft Hand, Right Hand Optional
Recommended Prop DiameterWood to 68"; Composite to 72"; Can Use Warp Drive Props
InductionCarbureted
Fuel PumpMechanical, Stock Corvair

Note:

Horsepower and Torque measured on dynamometer with air cleaner, full exhaust system and quiet muffler installed. Using a less restrictive exhaust system can exceed these numbers by 5%.

Turbo boosting is available on either motor; 5 psi will increase output by 25% on both motors with a weight increase of approximately 20 lbs.


Why Use a Corvair Engine?

  1. It is Time Proven

    Converted Corvair engines have been flying since 1960. In the past four decades, dozens of home builders have logged hundreds of hours behind them.

  2. It is Low Stress

    In the Corvair automobile, the engine produced 180 horsepower in the turbo-charged form. All 1964-69 model engines utilize the same crankshaft, rods, pistons, cases, etc. By flat rating the engine for 90hp continuous, the engine is only stressed to 50% of its rating in the automobile. No other auto engine conversion can make this claim. In the automobile, the engine redlines at 5,500 rpm. My aircraft conversion produces 75% power at half this rpm. These two facts form the cornerstone of the Corvair engine’s reliability as an aircraft power plant.

  3. It is a High Quality Engine

    The Corvair was the brainchild of Ed Cole, Chief of Engineering for General Motors, (the world's largest corporation at that time). GM put more R&D into this engine than Lycoming or Continental have put into any of theirs. All Corvair engines have forged cranks and rods, torsional vibration dampeners, hydraulic lifters and oil coolers as well as having all aluminum heads and cases. All of these stock components are suitable for use in a 100hp direct drive engine. I have never seen a cracked head, cylinder, case, crank or rod in the hundreds of Corvair engines I have inspected. It is a very strong engine.

  4. Good Engine Availability

    Aviation writer Richard Finch pointed out that General Motors made 1.7 million Corvairs in 10 years, compared to Lycoming taking 50 years to produce 230,000 engines of all models. Today, there are perhaps 100,000 Corvairs on the road, and there are at least five rebuildable engines for every good chassis. The Corvair Society of America (CORSA) is a nationwide organization of Corvair enthusiasts. It is similar in organization and membership to the EAA. There are several major Corvair-only parts suppliers who are all competitively priced. Rebuildable engines are readily available everywhere and one should cost about $100.

  5. It is Air Cooled

    Installing an air-cooled engine is easier than a water-cooled engine, especially in planes that were designed for air-cooled engines. Air-cooled engines do not have water pumps, thermostats, hoses, radiators and the associated hardware to mount them. Water-cooled engines can have trouble with air pockets in the cooling system as well as leaks. The dry weight of an air-cooled engine is a lot closer to its weight flying in the plane. Water-cooled engines will always be heavier than you first anticipated when looking at their dry weights.

    Dave Stroud of Canada replaced his Subaru EA-81 belt-drive installation with a 164cid gear-drive Corvair motor. Beyond a substantial performance improvement, the final installation was actually significantly lighter. Bob Lester of Fort Lauderdale, Fla., who converted his KR-2 from belt-drive EA-81 to direct drive Corvair, reports the final installation weighs 50 pounds less. These two examples illustrate that much of the weight information associated with liquid cooled installations is misleading.

  6. It’s Inexpensive

    This engine totally rebuilt can fly for less than $2,600 (Fletcher Burns built his for less than $1,100.) You might be able to find an O-200 for $2,600 (if you know someone), but that would not be a completely rebuilt engine. A Corvair engine that you completely rebuild is better than some pig in a poke. Don’t compare Apples to Oranges.

  7. It is Easy to Build

    I offer very detailed plans to convert the Corvair engine for aircraft use. The prop hub, the most difficult part, is shown in a detailed CAD drawing. This hub is also available from me completely finished, and beautifully anodized. I also offer numerous other parts and information which make the conversion easier. (Please see my Technical Support Page to learn about the genesis of The Conversion Manual. Please check my Online Catalog for more information on my products.) If you can build a plane, you can build a Corvair engine. The Corvair engine is far easier to assemble than a Continental or Lycoming. No impossible ADs or service bulletins, no cryptic manuals. The GM manuals have easy to follow directions as well as clear photographs.

  8. Parts are Readily Available

    If you need a cam gear for your O-200, where would you get one? What would it cost? How long would you have to wait? Would you end up using your old one, even if it was marginal? If you had a Corvair engine your cam gear would be as close as the nearest auto parts store, it would cost less than $40 and you would have it the next day. This is typical of Corvair engine parts. Specialty parts are available from the Corvair parts suppliers. These friendly people have been in business more than 20 years and are waiting to help you. You cannot get service like this from aviation companies.

  9. Technical Support

    All Conversion Manual owners have virtually 24-hour access to me via my my e-mail address, WilliamTCA@aol.com, or hangar phone number, (904) 529-0006.


Other Frequently Asked Corvair Questions

  1. Are parts available for Corvair engines?

    Yes, almost all of the internal engine parts are available from local auto stores. The few that are hard to find can be ordered from one of the Corvair specialty shops, which are listed in my Corvair Conversion Manual, available at the Online Catalog. My Conversion Manual also includes TRW and Sealed Power part numbers for all engine parts. All parts for my conversion are readily available from the Corvair parts houses or my Online Catalog.

  2. Why is a Corvair the least expensive 100hp auto conversion?

    Most auto engine conversions need to replace many of their internal parts to withstand continuous high output. These engines also need speed reduction units. The Corvair engine has neither of these problems. Most of the Corvair's internal parts, such as the crank, rods, cases and heads, do not have to be replaced with high strength parts: They are already high strength. Chevrolet offered the 164 cubic inch Corvair engine in several models from 110-180hp. They all have the same crank cases, rods, pistons and cylinders. The stock parts work well in a 100-120hp Corvair engine.

  3. How much does the Corvair engine weigh?

    A hand-prop Corvair engine weighs about 205 lbs. With electric start, it is about the same weight as an O-200 Continental. What you really need to look at is the power loading of the aircraft/engine combination. The power loading is defined as the gross weight of the plane divided by the horsepower of the engine. A KR-2's gross weight is 900 lbs. When powered by an 1,835cc 70hp VW, it has a power loading of 10.2 lbs./hp, while the same plane powered by a 2,700cc 100hp Corvair has a power loading of 9.0 lbs./hp. Planes that have lower power loading fly faster and climb much faster.

  4. What other planes would be good airframes for Corvair engines?

    Any airplane that has flown with an O-200 is a good choice. This would include the KR-1 & 2, Pietenpol, Sonerai, Tailwind, FlyBaby, VP-2, Zenair 601, Buttercup, Vision, Dragonfly, Q2, Boredom Fighter, Fisher, Hatz biplane, Christavia, Pober Junior Ace, Skycoupe and many, many more. If you have a specific plane in mind, e-mail me at WilliamTCA@aol.com or call me at (904) 529-0006.

  5. Pietenpols used Corvair engines and retained the stock cooling fan - should I?

    Both the stock cooling fan and a standard aircraft system will work. You can take 25 lbs. off the Corvair engine by using standard aircraft free air cooling. My parts and information are for either system.

  6. How smooth is the Corvair engine?

    It runs like an electric motor. There is no comparison to other engines with fewer cylinders. Several factors contribute to the Corvair’s smoothness: The stroke is less than 3 inches, the engines use a harmonic balancer, and the opposed six is a naturally balanced engine configuration.

  7. Are people satisfied with Corvair engines?

    Bernie Pietenpol built more than 20 planes. He was the first person to fly a Corvair engine. He could have used any engine, but he chose the Corvair. After his first flights with the Corvair engine, he used them exclusively for the rest of his planes. He said it was the smoothest engine he ever flew. In recent years, I have helped my customers re-engine a number of VW and Subaru powered airplanes. In all of these cases, the aircraft experienced performance improvements. In the case of the Subaru engines, every Corvair installation was lighter. I can think of no aircraft which was Corvair powered that was later changed to any other alternative engine. The only aircraft changed from Corvair to Lycoming was actually 10 mph slower after the switch.

  8. Do I need an electric starter?

    Virtually every Corvair motor built before I started my work was a Hand Prop motor. Some people, like our friend Jake Jaks, of Tallahassee, Fla., are going with hand prop motors for the ultimate in simplicity. I personally prefer electric start on an aircraft.

    After I developed an electric starter on the front of the motor, I later went on to develop one on the back. The Conversion Manual contains information on both of these. I was the first person ever to fly a Corvair motor with a starter on the back. The choice is yours, but if you wish to have a starter motor, it is inexpensive and there are styles to fit most installations.

  9. A friend of mine had a Corvair automobile and said it ran great but it leaked some oil. Will my Corvair engine leak oil?

    Corvairs originally were equipped with natural rubber gaskets and O-rings. With years of use these would dry out and then would leak. Today, Corvair gaskets and O-rings are made from Silicon and Viton. These materials will withstand more than 550 degrees F without loss of resiliency. Corvair engines built with Silicon and Viton gaskets will not leak oil.

  10. I heard that many of the Corvairs made were factory turbocharged. Could I use this on my plane?

    The factory Corvair turbo system cannot be used on flight engines. It is very heavy and the turbo is intentionally sized to only develop boost at rpm levels not used in flight motors.

    People frequently ask about turbo normalizing. Turbo normalizing to maintain sea level power to altitude only works on engines equipped with in-flight adjustable propellers. If you study certified airplanes carefully, you will never see a turbo without a constant speed prop. There are no in-flight adjustable props which are suitable for the Corvair motor.

    Turbo boosted engines can be built. A 20% increase in output would not overtax the cooling system on the motor. A modern turbo setup with an automatic wastegate, an item which is essential to operate the motor safely, is worth more than $1,000. It also requires a very expensive exhaust system fabricated from 321 stainless steel. The Conversion Manual contains more information on this subject, along with specific recommendations. But turboing is not necessary to have a good, powerful engine.

  11. Corvair engines rotate opposite to standard U.S. engines. Will I have a hard time locating a propeller?

    No. Corvairs have been flying since 1960. Almost all propeller manufacturers offer appropriate left-handed props at little additional expense. My Corvair Conversion Manual contains a list of all propeller manufacturers who build appropriate propellers for the Corvair engine. I also sell Warp Drive Ground Adjustable Carbon Props, which are listed in my Online Catalog. If you wish, the rotation can be converted to right hand; the cams used are available as reverse grinds at no additional expense.

  12. Is it difficult to fly an engine that turns left-handed?

    Absolutely not. It requires no additional skill. Ask anyone who has flown a VW engine or a Supermarine Spitfire.

  13. Which carburetor do you recommend?

    My Conversion Manual lists numerous choices and their sources, from $50 float carburetors to $800 throttle bodies. The most popular carbs are the MA3 and Stromberg NAS-3. The Monnett AeroCarb is also a popular option. The Corvair has successfully flown on dozens of different carburetors, and it is not sensitive to carburetion.

  14. Is cruising at 2,800rpm going to stress the Corvair engine?

    Not at all. The Corvair engine turns more than 3,000rpm at 60mph in the automobile. They can run for hours at a time over 4,500rpm. Asking the engine to produce 75% power, the brake mean effective pressure (BMEP) is lower at 2,800rpm than at 2,000rpm.

  15. How do I get my name spelled correctly on your Web site, or submit my photo to the Flying Planes page?

    To suggest changes or updates to www.FlyCorvair.com, please e-mail Aviatrix. I encourage anyone who has built and flown a Corvair to complete a Corvair History Questionnaire and return it with photos via e-mail to WilliamTCA@aol.com or snail mail (please specify if you want photos returned rather than added to the albums I take to fly-ins) to William Wynne, 5000-18 HWY 17 #247, Orange Park, FL 32003. Thank you.


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