3,000cc/Billet Crank Shortblock, Destination: Waiex

Builders,

Below is another look at a high quality Corvair. This particular engine is in my shop right now, but is soon headed to its owner. The engine is something of a ‘kit’, and it is a clone of the engine in Dan Weseman’s  Panther. After some planning with the owner, we decided that it made the most sense for me to find a core for him in Florida and perform all the modifications to it before sending it. The owner is a skilled mechanic, but opted to have us assemble the case and install the Weseman Billet crank and Gen 2 5th bearing. We are shipping the rest of the parts, the 3,000cc Piston/rod/cylinder kit and a set of Falcon heads, along with the gold components to finish the engine. The total isn’t cheap, but it is a good value. Keep in mind the Builders goal is to have an absolutely first class engine for his Waiex. The Corvair covers many builders needs, this particular engine is a good representation of the upper end of the spectrum of options. Although this engine was planned as a ‘cost is not a consideration’ build, it is worth nothing that the engine is almost entirely made of made in the USA parts, and it still costs only 40 to 60% of an imported engine. Corvairs are not for everyone, but there are good reasons why they make sense to the builders who choose them.

Above, the engine in a case assembly stand on my work bench. If you look closely, the Weseman Billet crank is visible. In our numbering system, this is part 1001(B). This engine has a new OT-10 and a California Corvairs Billet cam gear. The 5th bearing is a Gen 2 Weseman bearing. The tape over the Hybrid studs is part of the vastly simplified installation procedures of the Gen 2 design. This Case has already been bored for the 3,000 cc Cylinders. This engine uses aftermarket rods with floating pins, also sold by the Weseman’s.  Although many people think of Corvairs as “rebuilt” or automotive engines, The only parts that came from the car that remain in this particular engine are the case, the bare head castings, the rear oil case casting and some miscellaneous small hardware. Everything else is new, and the great majority of it, like the crank, pistons, cylinders, oil system etc, was all specifically designed for flight engines. I have never shied away from the term “automotive conversion engine” because it is an accurate description of the Corvair. We have converted this engine internally to meet the demands of being an actual aircraft power plant.

Throughout much of the history of experimental aviation there have been advocates of taking a an engine straight out of a wrecked car and putting some external systems on it and running it in a plane. Sounds attractive to people looking for a ‘bargain’, but these engines typically have a very poor track record. Flying in a plane is a demanding and specific task that automotive engines in their pure form are not designed for. You can get away with it when you shoot for 50hp out of 200 cubic inches (model A) or even 75HP out of 164 cid (original Bernard Pietenpol Corvair Conversion).  In recent years there have been many people who claimed that you could get 100 or 115hp out of a 110 cid Subaru pulled straight from a car. Today there are car engines aiming for 100hp out of 79 cubic inches. There have never been a shortage of bargain hunters to buy into this ‘free lunch’ mentality.  I have long said that I am in aviation to tell builders what they need to know, and this is often very different that what people want to hear. Reasonable people understand that driving up the HP/cubing inch and raising the RPM to 5000 or 6,000 rpm, at the same time as trying to get away with basic car parts inside is not a formula for longevity nor cooling. 

Philosophically, the Corvair is in the same line of thought as the Jabaru 3300 (201cid/120hp/3,300rpm) and the UL-350 (215cid/130HP/3,200rpm). Neither of these two engines is a “Car” engine. they have internal components designed for the stress of flight duty, Just like the Corvair.  If you consider the examples of Lycoming and Continental, The Corvair is using the same basic layout and philosophy of the majority of successful engines.

There will always be people who point to rotax 912s and say they are 100hp from 80 cubic inches. I respond by saying that they really are purpose-built engines, and they have a lifespan and a cost per hour that I don’t find to be a good value. Everyone thinks that 912’s are an incredibly prolific engine, but consider that they have made 40,000 of them total in several decades. Continental has made far more O-200s than that, and GM made more than 40,000 Corvairs a month in 1964 alone. Another issue to consider is that I have worked on O-200’s that have been overhauled several times and had more than 6,000 hours on the basic components, parts that were designed to be rebuilt several times (just like a Corvair).  I have heard very few stories of people ‘rebuilding’ a 912. It isn’t that kind of engine, it is much more akin to a disposable appliance. This doesn’t bother most people, but it isn’t the kind of engine I want on my plane. Think it over and come up with your own answer that makes sense to you. Its your project, your choice. -ww.