Corvair Myths

A great book to add to your Corvair Library is “Corvair Secrets“, written and published by the late Bob Helt. Bob published many books on the Corvair and all are worthy of a read.

For today, we want to crack open “Corvair Secrets” and share one with you. Corvair Myths.

It is strange how some stories get started and then continue to be told despite how little truth there is to them. It would seem that some people just want them to be true no matter how wrong the stories are. We call these stories “Corvair Myths” because there are no facts to back them up, yet people continue to believe them.

Corvairs had sodium filled exhaust valves

While Corvair exhaust valves do indeed run at high temperatures, there is no evidence that there were any valve problems after some early model failures were fixed. Sodium filled valves are expensive, and not in general use in American cars. Because the purpose of the sodium was to melt and be thrown around inside the valve for increased cooling, larger than normal valve stems were required to accomplish this purpose. The Corvairs all had relatively narrow stems and could not have accommodated a pocket for the sodium. In addition, no factory or aftermarket literature refers to sodium filled valves for any Corvairs. Sodium valves were not used on any Corvairs either from the factory or aftermarket.

Factory supplied Bias-Ply tires were larger than currently available radial stock replacements

A strange quirk of fate. The old style bias-ply tires were somewhat like balloons. When mounted and filled with air they did look big, just like an inflated balloon. But when the weight of the car was placed on them, they collapsed (at least at the bottom). So if you were to place side-by-side, for example, two tires each mounted on a rim and inflated, one a factory 7.00×13, and the other its replacement, a radial 185/80R13, the 7.00×13 tire would appear to be larger than the other. But on the ground under the same weight car, the bias-ply tire collapses more, so they both turn at almost the exact same number of revolutions per mile (840 vs. 843). This means they both have almost the exact same rolling circumference. Thus, both of these tires are the same size as far as the car is concerned, and the speedometers (and odometers) will read the same too. So while the 7.00×13 tire may appear to be larger it actually isn’t. It’s just a visual quirk.

There were four cylinder Corvairs

Well of course, you know how this one got started. They took a look at a factory stock 140 engine and saw those four runners on the air cleaner leading to four carburetors. Four carburetors must mean four cylinders, right? Wrong!!

Porsche designed the Corvair engine

This is totally false per Chief Corvair Engine Designer, Bob Benzinger. According to him, Porsche (and VW too) had absolutely nothing to do with the Corvair engine design. To emphasize his point, Bob points out that the four-cylinder Porsche and VW engines all had their exhausts vented to the ends of the engine for easy flow. But the Corvair couldn’t do this since it had a middle cylinder on each bank. Thus, the design had to be different. And to further explain his point, Bob wondered if maybe the opposite contention might be true since Porsche didn’t come out with their six-cylinder engine until their 1965 model year, a five full years behind the Corvair. Maybe Porsche borrowed some of the Corvairs features and learned from the Corvair’s design. We know that Porsche bought a few Corvairs for their evaluation (see main photo at top of this post). So maybe Porsche borrowed from the Corvair’s engine design and not as the myth states.

No 140 engines were produced in 1967

While Chevrolet did discontinue the 140-hp engine at the start of the 1967 model year, it was reinstated in January 1967 as a COPO special order primarily at the request of Don Yenko, who was General Manager of the Yenko Chevrolet dealership in Cannonsburg, PA. Don needed the 140 engines for his Stingers (Stingers used only 140 engines), and he was able to convince Ed Cole of the favorable publicity that would result. He took delivery of 25 140 engine powered Monzas in March of 1967. And very favorable was the publicity, when in 1967 a Yenko Stinger won the SCCA D/P Class National Championship. What a wonderful and little known fact. A national SCCA championship class win for the Corvair.

(ed note: It may have been Pete Estes that green lit the 140 production for 1967 as he was the GM of Chevrolet at the time while Ed Cole was the President and CEO of GM)

Turbo engines had a muffler that was designed to be restrictive

Just the opposite! Yes, Corvair turbo engines were boost limited by their design so that waste gates and blow-off valves were not needed. But this boost-limiting effect (to limit boost to a maximum of about 10 PSI) was mostly performed by virtue of a restrictive carburetor Venturi, and not the exhaust system. In fact, a free-flowing exhaust muffler is essential to proper operation of a turbocharger system. Any back pressure lowers the efficiency and robs horsepower. Yes, the pipes from the engine to the turbine are somewhat restrictive by nature of their diameter, but this is to keep the exhaust gas velocity high and reduce the heat loss. Exhaust gas leaving the turbine, flows in 2 1/2″ large pipes to the free-flowing muffler to reduce back pressure and maximize power.

And here is a little known fact: The Corvair turbo muffler was a special free-flowing oval design to reduce back pressure. The secret was that the turbine itself lowered the exhaust noise so much that the muffler then had less work to do and thus could be designed to be less restrictive. The Corvair muffler was the first of many free-flowing “turbo mufflers” and set off somewhat of a turbo muffler craze in the marketplace. For a while in the early 1970’s, many different aftermarket turbo-type mufflers were tested by several popular car magazines. Hot Rod magazine published a test report in October 1973 on performance mufflers then available and reported that the Corvair turbo LM muffler was the best with the least restriction.

The Early Model Corvairs used manual transmissions that were either built at the Muncie plant, or built by Borg Warner

Not true! In fact, all Corvair manual transmissions were designed and built at the GM Saginaw (Michigan) plant. The 1966-1969 manual transmissions were called “Saginaws” because they were based on a more common big-Chevrolet design. But all Corvair manual transmissions were Saginaws if you consider where they were designed and built. No Corvair manual transmissions were ever built by Muncie or Borg Warner.

Corvair engines actually developed their advertised horsepower

During the years of Corvair production it was common practice for the car manufacturers to rate their engines about 20% higher than the actual “As installed” horsepower the engines developed. This Advertised Horsepower was the power developed under laboratory conditions where no power was required to turn the cooling fan and no power was lost with a muffler system, plus a few other special techniques to fudge the horsepower to a higher value. For example, the actual As Installed horsepower of the 110 engine was approximately 83-hp. Similarly, the 140-hp engine produced about 109 As Installed horsepower.

What are some Corvair Myths you have heard over the years that Bob didn’t mention? Have you heard any of these Myths? Comment and lets hear those myths!