Didn’t Porsche Design the Corvair?

Just how did the Corvair come to be? Of course, said many, it was designed by Porsche. Numerous influences, including a powerful tank engine, shaped Chevy's fear-engined compact. And Porsche was involved--in an unusual way.

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December 10, 2015

It’s an idea that refused to die. When Chevrolet introduced its Corvair in the autumn of 1959, rumors were rife. Porsche designed the Volkswagen, didn’t it? And wasn’t the Corvair a grown-up Volkswagen? And what did Chevrolet know about designing air-cooled rear-engined cars anyway? Thus it was obvious: Porsche must have designed the Corvair!

The idea had some legs because it would not have been the first time that Porsche designed an American car. Between 1952 and 1954 it engineered and built prototypes of its Type 542, a four-door sedan for Studebaker with 120-degree V6 engines, air- or water-cooled to choice. This was a front-engined car in the conventional style, albeit with unibody construction and independent suspension at all four wheels.

Anticipating that such a full-sized auto might not be the answer to Studebaker’s prayers, Ferry Porsche, the head of Porsche AG, also suggested a smaller car, his Type 633. His proposal showed a notchback two-door sedan with a Porsche-like front deck and a 2.0-liter flat-four engine behind the rear wheels. Air-cooled, it had hemispherical cylinder heads. Torsion-bar springs and 13-inch wheels were suggested for an admirably practical 14-foot-long car.

Ferry Porsche later pointed out with a knowing smile that many of the Type 633’s features and dimensions foreshadowed those of the Corvair. Its wheelbase was shorter at 102.4 versus 108.0 inches, but its track and width were similar. Although it was shorter, its seating would have been adequate with a height of 55.1 inches against the Corvair’s 51.5. At just over 80 horsepower its engine output was to be similar with a top speed much the same at 90 mph. Porsche posited a weight of 2,112 pounds against the Corvair’s 2,420.

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Similarities notwithstanding, the Type 633 was not a Corvair precursor. Edward N. Cole, who headed Chevrolet Engineering when the project got under way, confirmed this. “I didn’t talk to anyone at Porsche,” said Cole, “but I did speak to some of the people at Volkswagen. I had known (VW’s managing director from 1948-1968) Heinz Nordhoff quite well when he was at GM.” A senior executive at Opel in Germany in the 1930s, Nordhoff had liaised frequently with his American counterparts. He had no reason to withhold information from Cole, who would be competing in an altogether different segment.

Planes, Tanks & Cars

With Porsche locked into a consulting contract with Volkswagen after the war, Nordhoff may well have told Ferry Porsche about his conversations with Cole. Although its agreement with VW prohibited Porsche from working for any rivals in the Beetle’s engine-size category, this wouldn’t have barred it from designing a larger-engined car for GM, just as it had for Studebaker. But it didn’t. A comprehensive list of Porsche project numbers show none that could even remotely have been attributable to the Corvair project.

Porsche, however, did ultimately figure in the Corvair’s gestation. Here were Ed Cole’s thoughts on its engine: “Because of its placement the Corvair engine required a low profile, although it was not necessary that it be opposed. Then the question was: should it be a four or a six?” At that time the flat six was more typically an aircraft engine with Franklins, Continentals and Lycomings common in this style.

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“In 1950 I logged about 300 hours in a Continental powered C Bonanza,” Cole recalled for L. Scott Bailey, “flying many times on instruments under unpleasant conditions, and I certainly got to know the great reliability this engine had and still has for that matter.”

Another influence was a military project undertaken by the Cadillac Division of General Motors. “In 1950 we were asked by the government to develop a facility to produce another light tank,” Cole explained. At the time he was a senior Cadillac engineer clearly destined for great things. “This was the T41El, later the M 42, and for this we used an 896-cubic-inch Continental horizontally opposed flat six. So once more we had exposure to an air-cooled engine—a configuration that was straightforward and simple. Naturally all our engineers working on the project became very familiar with this engine.”

Although Cadillac’s own V8 engines had successfully powered tanks in World War II, Cadillac couldn’t challenge the Army Ordnance Department on the choice of Continental as the supplier because the Muskegon, Michigan-based engine specialist had been developing a new engine expressly for tank use. And it was quite an engine. Its 14.7 liters were deployed in six flat-opposed cylinders powering a four-main-bearing crankshaft.

Continental’s Type AOS-895-3 six was shot full of high-tech features. Each finely finned cylinder had two vee-inclined overhead valves, closed by triple springs and operated by rockers from a single overhead camshaft. Rotating the cams and all the main organs were spur gears and shaft drives that would look familiar to any connoisseur of Porsche’s racing engines. At the six’s front end, twin-throat downdraft carburetors on left and right fed the inlet of a centrifugal supercharger—highly exotic equipment that bolstered the top end of the torque curve.

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Also driven by the shafts was another racing-Porsche-like feature: a fine-bladed flat cooling fan above the cylinders. It drove air down through the cylinders and out to the sides through a pair of oil coolers. It would reappear, belt-driven, on the Corvair. A pair of Bendix-Scintilla magnetos fired a dual ignition. The result at 2,800 rpm was 500 hp gross, which delivered 380 hp at the same speed as installed. The vital element, torque, was 975 lb-ft gross at 2,250 rpm, falling to a still-strong 825 lb-ft at 2,000 rpm when installed.

This advanced engine made an impact on Cole, with whom the buck stopped when it was time to recommend a power unit for the compact Corvair, nurtured in its early days as “Project Holden.” This was convincing because Chevrolet often did design work for Holden, its Australian cousin.

“From talks we’d had with engineers at Continental and elsewhere where fours had been built and our experience with the tank operation,” said Cole, “the conclusion came quickly. From the point of view of smoothness and carburetion the six was easier to handle. And, all things considered, it didn’t offer too much of an economic barrier. Everybody voted that the Corvair engine ought to be a six.”

The choice of a flat-six engine was unusual at the time with few having been designed specifically for cars. One was an experimental Mercedes-Benz engine of the mid-1930s for a front-wheel-drive prototype, designed by the team of Hans-Gustav Röhr. Another was the Tucker 48’s flat six that, in its final design, was a liquid-cooled conversion of a Franklin airplane engine.

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Around that time, in 1948, Porsche schemed a flat six for a client in Argentina. Air-cooled, its 2.0-liter Type 372 had pushrod overhead valves and four main bearings. Never actually built, the project remained a secret. Zuffenhausen’s own six-cylinder 911 was almost a decade in the future when Chevrolet had to decide on the configuration of the Corvair’s powerplant.

The First Flat Six-Powered Porsche

In the early summer of 1957, Chevrolet Engineering bought a Porsche 356 1600 coupe. We can date it fairly precisely because it had the new teardrop-shaped tail lamps introduced that spring but not yet the exhaust outlets in the bumper overriders of the 1958 models. Its engine was dropped out and put on a dynamometer to be subjected to instrumented tests of temperatures and clearances. Information thus gained helped the Corvair engine’s designers, who were having special problems cooling the center cylinders. This was, of course, new ground where the Porsche example couldn’t help.

The Corvair design that evolved could hardly avoid looking like a cross section of a Volkswagen or Porsche engine with its pushrod valve gear and camshaft below the crankshaft. In this it was unlike the flat-sixes produced for aircraft that usually had the camshaft above the crank. The Corvair’s rectilinear split crankcase with its flared bottom had more of an aircraft flavor, however. Like aircraft sixes and the Continental tank engine, the Corvair had four main bearings.

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The engine’s overall configuration in detail was the work of Chevrolet’s Adelbert “Al” Kolbe, who applied for a patent on its layout on December 31, 1958. Distinctive features were Chevy’s stamped-steel rocker arms, introduced in 1955 on the small-block V8, and hydraulic zero-lash tappets to overcome the problem of differential expansion caused by heat in an engine with finned iron cylinders and aluminum heads. Unlike the Porsche and VW engines, the gear drive to the camshaft was at the engine’s flywheel end.

Unusually, for what was seen as an economy-car engine, Chevrolet fitted each cylinder bank with its own carburetor. Designer of its crankcase ventilation Bob Benzinger said that this was done “to place the carburetors as close as possible to the inlet ports, achieving good response and maintaining high volumetric efficiency.” This decision showed greater influence by Porsche than by Volkswagen, which made do with a single central carburetor. A penalty was convoluted induction with a choke fitted to the central air cleaner. From 1962, each carburetor had its own air cleaner.

For engine cooling Chevrolet adopted the Porsche and VW solution by choosing a Sirocco-type forward curved centrifugal fan. Instead of mounting it vertically as in those German examples, however, it placed the blower flat above the engine’s center, following the Continental’s example. This best suited the car’s design, which required a low rear deck.

Even if Porsche had practically engineered the internals of the Corvair, there was no doubting the American origins of its shape and style. This was created at the end of the influence of Harley Earl, who left the office of GM Vice President of Styling Staff in December of 1958. It bore the Earl trademark of lowness calculated to emphasize length. But its styling was the work of Ned F. Nickles, working under the direction of William L. Mitchell, Earl’s successor as Styling VP. The result was a uniquely elegant and appealing small car.

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As the Corvair took shape under its “Holden 25” code name, its engine was ready for road testing before the first prototype cars. Waiting to accept it was none other than the same 1957 Porsche 356 whose engine was used for cooling experiments. At Chevy’s freshly minted Engineering Center at Warren, Michigan, the first Corvair drivetrain was installed in the Porsche. Complete with Chevy’s manual transmission, effectively creating the first flat-six-powered Porsche ever. The Corvair six fitted it surprisingly well. Eager as a kid, Ed Cole hopped in and belted away.

Cole vividly remembered that first encounter with the Corvair-powered Porsche: “Perhaps the greatest thrill for me personally was the first concrete evidence that the Corvair really came up to our hopes and expectations,” he recalled. “This came when I test-drove a modified Porsche which contained the new Corvair engine while we were waiting for our first pre-test prototypes of the Corvair to be completed. I drove this car at the GM Technical Center and Milford Proving Grounds in late 1957 and at Pikes Peak, Colorado in early 1958. She ran beautifully. I knew that we had a winner.”

A Source of Inspiration

Ferry Porsche was, of course, interested in the Corvair. Through Huschke von Hanstein, his director of PR and motorsports, he arranged to buy one of the first ones made. It would be invidious to suggest that Chevrolet’s effort influenced Porsche, but it cannot be overlooked that Leonard Jäntschke’s first prototype engine for the future 911, the Type 745 of 1961, had a four-bearing crankshaft just like the Corvair’s. For its final design, though, Porsche adopted seven main bearings instead. It was a decision that secured the long life of Porsche’s flat six.

Ferry Porsche’s Corvair wasn’t the only one running around the streets of Stuttgart. Dan Gurney, one of Porsche’s Formula One drivers in 1961-1962, brought one over to show what the New World could accomplish in car design. Porsche later used some Corvair Lakewoods to test its first flat sixes.

The many travails of the Corvair as released for the 1960 model year are well known. Mistakes were leaving off the front anti-roll bar to save money and allowing the proportion of weight on the rear wheels to rise too high, something that Ferdinand Porsche controlled rigorously in his designs. Steering response was too slow, deliberately so people would not excite it too much—not a good decision. The requirement for sharply differing tire pressures front and rear did not accord with American ideas of car maintenance.

However a road test in Stuttgart-based magazine auto motor und sport declared the Corvair “Europe’s lost opportunity.” They understood what Chevy had achieved in such a radical departure from the American norm. And when the 1965 model appeared, with its superb styling and Corvette-inspired rear suspension, the Corvair achieved its potential. Disappointingly, however, GM’s management decided to let it fade away instead of exploiting one of the most charming and distinctive American cars ever made.

Also from Issue 234

  • The 2016 Boxster Spyder
  • 991 & 964 Targa Face Off
  • Original Porsche 550 Spyder Drive
  • Market Update: 1952-1965 356
  • Pushrod-engined 356 Carrera GT Speedster
  • Barn Find, Jersey Style 911
  • Rennsport Reunion V
  • 911 Suspension Evolution
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