Chevy Corvair

Chevy Corvair

The Corvair was part of GM's innovative A-body ("Z"-Body from 1965-on) line of cars, but this was by far the most unusual, due to the location and design of its engine. It was a air-cooled flat / opposed rear-engined vehicle inspired by the Volkswagen Beetle and the Porsche 356 Speedster. This was quite radical for American cars at the time, in contrast to later compact Chevy II / Nova and subcompact Vega. But instead of an iron 4 cylinder engine common to imported cars, the Corvair had an aluminum, air-cooled 140 in³ (2.3 L) flat-6 engine. The first Chevrolet Corvair engine produced as little as 80 hp (60 kW), but later developed as much as 180 hp.

History
The Corvair's innovative flat-6 engine left room for the spare tire, creating even more room in the forward trunk.The Corvair name originated as a fastback show car in 1954, which, like many Chevrolet concept cars of the period, including the Chevrolet Nomad and Chevrolet Impala, was based on the Corvette. The design was championed by Ed Cole, Chevrolet's chief engineer in the early 1950s and general manager in the late 1950s, as an answer to the growing popularity of small, lightweight imported cars.

Design began in 1956 under the auspices of Ed Cole, and the first vehicles rolled off the assembly line in late 1959 as part of the 1960 model year (in which it was named Motor Trend magazine's Car of the Year). For 24 hours, two Corvairs were tested at the Riverside International Raceway in Riverside, California. One car rolled over, but the other completed the drive, only losing a quart (1 L) of oil (Source: Riverside Raceway Palace of Speed by Dick Wallen).

The Corvair enjoyed a ten model year run, and was finally discontinued in May 1969 due to plummeting sales. A variety of factors contributed to the model's 96% drop in sales from 1965 to the last 1969 models. The Corvair faced increasing competition from the Ford Mustang and other 'pony cars' - ironically, a market pioneered by the 1960 Corvair Monza. Safety issues were raised, especially by Ralph Nader's 1965 book Unsafe At Any Speed. The car's design was costly to produce and did not command a premium price on the showroom floor. Engineers experienced difficulties adapting the basic engine design to the tighter emissions standards proposed for 1972. Lastly, a general lack of interest at General Motors, including an almost complete lack of advertising from 1967 onwards (the company's 1969 Corvair showroom brochure was a mere 4 pages long, and the 500 Sport Coupe wasn't even illustrated) contributed to the model's demise.

The Corvair was a successful model for Chevrolet, with annual unit sales exceeding 200,000 for many years. Chevrolet deliberately designed the Corvair as a radical departure from the conventional Chevrolet. The rear engine offered enormous packaging and economy advantages, providing the car with a lower silhouette, flattening passenger compartment floor, obviating the need for power assists, reducing the need for air conditioning (due to the absence of engine heat blowing over the passenger compartment), and offering dramatic improvements in ride comfort, traction and braking balance. The radically different design also attracted customers from other makes, primarily imports. This was an important, and often under-emphasized, driver for the Corvair's success.

Unlike the Falcon and Valiant nameplates, whose conventional designs tended to poach customers from the cheaper but profit-driving full-size models from their respective manufacturers, the Corvair siphoned customers from makes such as Volvo or VW. Because such customers had not been likely to contemplate a larger Chevrolet Biscayne (which cost only slightly more), each Corvair sold did not translate into a Biscayne that was lost. This was in direct contrast to the situation at Ford, where the Falcon nearly ate its maker alive by stealing sales from the basic large Ford sedan. Corvair sales were almost entirely "extra business" for Chevrolet.

General Motors did have plans for a 1970-on model Corvair, essentially a re-skin of the 1965-69 body with new exterior sheetmetal. The car likely would have debuted as a "1970 1/2" model, much as Corvette and Camaro did for 1970. The overall appearance of this third generation Corvair was very similar to the 1973 GM A Body intermediates-- particularly the 1973 Pontiac Grand Am. It retained Corvair proportions, with a rounded sweeping body, terminating in a tapered tail with a glassy roof, featuring fixed quarter windows. This program progressed past the point of full scale clay models before being dropped in early 1968. One interesting project at GM was the Turbo Hydramatic 350 transmission, introduced in the 1968 Camaro and later adopted by most Chevrolet models. It was laid out in a manner that would permit its use in the Corvair, unlike the Turbo Hydramatic 400 and most other designs. Had the 1970-on Corvair been built, it is clear this transmission would have been adapted for the Corvair. The last word on the 1970+ "third generation" Corvair was, "Mr. Cole (GM President Ed Cole, ex-Chevrolet General Manager during Corvair development) is not enthused about this program..."[citation needed]

In what may be the automotive industry’s greatest irony, NHTSA, the federal agency created from Nader’s “consumer advocacy,” investigated the Corvair and issued a report in 1971 clearing the car’s design. But that was two years after the car went out of production, and not nearly as headline-worthy as Nader’s initial claims.

Part of Nader’s evidence against the Corvair was a promotional film created by Ford Motor Company, in which a Ford test driver purposely turned the Corvair in a way to make it spin around. Such films were not uncommon. GM also had films showing the Ford Econoline pickups standing on their noses under heavy braking.

Engineering
The Chevrolet Corvair engine, unique for an United States car, presented a different set of requirements for mechanics, many of whom treated the engine in the same way as they would an engine of normal design, leading to problems.

An engineering weakness not generally highlighted related to fumes and gases entering the passenger area via the heater system, a problem endemic to an air-cooled engine that uses heat radiated from the engine directly to heat air for the passenger compartment. Carbon monoxide and other noxious or deadly gases could enter the passenger areas if exhaust system gaskets aged or failed using this system, since the gaskets were inside the heater box air intakes and air for engine cooling was used for passenger–compartment heating when the heater was on (or leaking). The 1960 model Corvairs used a GM Harrison division gasoline heater located in the front trunk area as its standard heater, similar to the Eberspächer heater offered as an auxiliary heater by Volkswagen as a dealer-installed option. This feature became optional in 1961 and was dropped in 1965 due to weak consumer demand.

Chronic oil leakage from the pushrod tubes, caused by GM's poor choice of pushrod tube seal material, also contaminated the passenger heating air. That air might also become noxious if a 6-inch (152 mm) wide rubber seal almost 16 feet (5 m) long, located between the engine assembly and the body, was not maintained in like-new condition. Another common problem in the earlier years was oil leakage caused by dissimilar metal thermal expansion on the aluminum–and–steel engine. Chevrolet wrestled with several problems of this nature the entire time the Corvair was in production with varying degrees of success.

The interior air would also be contaminated if the voltage regulator allowed an over-voltage condition and the original battery vent hoses were not attached. The battery, which was mounted in the engine compartment, could emit hydrogen if overcharged. Chevrolet installed special battery caps and hoses that vented the battery to air outside the engine compartment, but these were often discarded by owners during the car's life.

The Volkswagen Beetle (Type I), another automobile with an air cooled engine, had a heater system which better isolated fresh air from engine cooling air fumes, and was only susceptible to carbon monoxide contamination from the two heat exchanger to muffler seals at the rear of the engine, as opposed to the eight exhaust joints in the Corvair system. This air contamination problem is illustrated by the fact that many American cities' taxi regulations had prohibited air-cooled engine cars from being used as taxicabs when they derived their heated air from engine exhaust heat, decades before the Corvair and VW Beetle entered the market.

A criticism in Lawyer Ralph Nader's 1965 book concerned the steering column design. Like most cars of its era, the Corvair's steering column was rigid and could impale the driver in a front-end collision. While the Corvair's steering box was mounted ahead of the front cross-member, it was well behind the frame horns, in what would later be called a "crumple zone," and could, in a severe front-end collision, push the steering column and steering wheel toward the driver. In practice, most driver chest injuries were sustained due to the lack of a shoulder belt, rather than steering column intrusion. Any increase in risk of injury due to steering column intrusion in a front-end collision was, however, more than offset by the absence of an incompressible engine and transmission in the front of the vehicle, which commonly intruded into passenger compartments on vehicles of the era. Chevrolet, aware of Nader's criticism, changed the steering shaft to a two-part design with a frangible joint late in the 1965 model year, and a collapsible steering column was provided in 1967, towards the end of the model's life span.

The criticism of the 1960-'63 Corvair handling was not entirely groundless. Although it was a competent handling vehicle as delivered from the factory, with characteristics quite similar to many imported cars, such as Mercedes and Volkswagen, which also used swing axle suspensions with similar handling attributes, there was room for improvement. Advertising in 1960 from domestic competitors showing the results of shooting an arrow weighted at the rear end missing its target widely did little to foster confidence in many minds about the stability of the car.

Chevrolet had tailored the handling of the Corvair by using very wide tires for such a light car (6.50-13, considered wide at the time, even contemporary Corvette used only a 6.70) to bear the weight of the rear and reduced front pressures by about 11 psi to increase front slip angles to balance traction and maintain confident control. If this pressure difference was not maintained, the handling would suffer as in very hard cornering, the rear slip angles would exceed the front slip angles and could lead to spin out or loss of control at very high speeds where the car is travelling dozens of feet per second and small changes in the rate of drift between the opposing ends of the car translated into a departure from the driver's intended course down his lane or in some cases, the road.

Swing axles were a common suspension design during the Corvair era- Millions of Ford pickup trucks were sold well into the 1990's using 'Twin I Beam' which is a swing axle. The advantages of swing axles are quite numerous; very compact packaging, tremendous strength and durability on rough surfaces, very good isolation of road harshness and a very smooth ride due to the camber changes forcing the tire carcass to absorb blows sideways as well as radially on severe bumps.

The primary deficiency of swing axle suspensions is they create a high 'roll center'; the theoretical point the car center of mass pivots around as it leans in cornering. Although a high roll center reduces body roll in cornering, and reduces sensitivity to cambered roads and crosswinds- all good attributes- high roll centers create 'roll stiffness' which is resistance to body roll. This roll stiffness transfers outboard weight shifts in cornering to the outboard tire in a corner. Pre-1965 Corvair has a rear roll center approximately 13" above the road surface and front roll center just slightly below the road surface. This concentration of roll loading on the rear wheels means as the severity of cornering loads increased the weight was transferred to the already heavily loaded rear tire and the car would progressively carry a larger proportion of the car weight on the outboard rear wheel, increasing its slip angle and eventually pushing the car into lift-off oversteer.

Chevrolet had considered adding a front anti-roll bar for the original 1960 car, which would have shifted a significant part of this weight transfer to the FRONT outboard tire and reduced the rear slip angles considerably in severe cornering, but the extra cost ($6 per car is often cited) and confidence in the tire pressure differential adequately compensating for the inclination for oversteer led GM to delete the anti–roll bar from production models. This false economy was to come back to haunt GM later. The anti–roll bar did become available as an option in 1962, and was made standard finally in 1964. The 1964 rear suspension was modified considerably with a transverse leaf spring carrying much of the rear weight and vastly softer coil springs, in an effort to significantly reduce roll stiffness at the rear of the chassis. The redesigned 1965 suspension was a total solution, cutting the rear roll center down to half its previous height, reducing rear roll stiffness very significantly with fully articulated half-axles that offered constant camber on the rear tires in all driving situations. Although much is made of the 'jacking' (tendency for swing axle suspensions to go into very severe positive camber in extreme corners) and large camber changes generally during suspension travel in swing axle suspensions, the bias ply tires used at the time were very insensitive to camber and did not have very significant reductions in cornering power at high camber, unlike belted and radial tires which became commonplace later on.

Contemporary Volkswagens, Renaults, Porsches, and other rear-engined cars all used swing axles. As Corvair was designed to avoid terminal oversteer by using very low air pressure in the front tires, typically 15 to 19 pounds force per square inch, so that they would begin to understeer (increase slip angles faster than the rear) before the swing axle oversteer would come into play, this pressure was quite adequate for the very lightweight Corvair front end on the already quite wide tire. Owners and mechanics, either through ignorance of the necessity for this pressure differential between front and rear or thinking that the pressure was too low for the front, would frequently inflate the front tires to more "normal" pressures, thus ensuring that the rear of the car would oversteer. It should be mentioned that the Corvair is by no means unique in requiring dissimilar front and rear tire pressures for normal controllability; even the front–wheel–drive Cadillac Eldorado years later used very low REAR pressures (16 psi) to balance handling.

Although Nader probably overstated the severity of the handling problems, as was later found by US National Highway Traffic Safety Administration investigators, Chevrolet made changes to the suspension: in 1964, adding a transverse leaf spring extending between the rear wheels to limit rear wheel camber change. In 1965 the Corvair got a state–of–the–art fully independent rear suspension closely resembling that of the contemporary Corvette, even sharing some components. These changes were, however, viewed by critics as Chevrolet's recognition of problems with the original design.