1956 Corvette Impala

Five-passenger Luxury Sport

By David W. Temple

A Corvette-like dream car graced a turntable at the five venues of the 1956 GM

Motorama. It was the Corvette Impala, an automobile styled to give a little sports car “flavoring” to a five-passenger luxury car. The dream car’s toothy grille and rounded quarters revealed its styling was influenced by the newly restyled first generation Corvette. A special brochure about the Corvette Impala stated the car “incorporates wholly new considerations in fine passenger car design from the standpoint of sleekness, safety, and luxury.”

Named for the agile African antelope, the fiberglass experimental car designed by Bob Cadaret and Carl Renner had a 225hp Super Turbo-Fire V-8 engine coupled to a two-speed Powerglide. The V-8 was modified with a 9.25:1 compression ratio and a high-lift camshaft. Spent exhaust exited through a dual set of pipes passing through the driveshaft tunnel and into a transverse mounted muffler with dual outlets projecting through the lower rear body panel.

Styling of the Corvette Impala foretold that of the Chevrolet Impala which debuted for the 1958 model year. In fact, at one point the toothy grille was proposed for use on the new model, but was abandoned due to cost considerations. Even so, the integral bumper and grille theme was kept. Other styling features of the Corvette Impala included a tinted “Panoramic” wraparound windshield curving up into the pale blue-tinted brushed stainless steel roof, a wraparound rear windshield, beltline dip near the reverse slant C-pillars, and chrome-plated wire wheels with knock-off hubs. All of these – with the exceptions of the wire wheels and the brushed stainless steel roof – were adopted for the production car. Its nose emblem was very close to the production type used for the 1958-60 Corvettes, but with the name “Corvette Impala” embossed circumferentially around the crossed flags.

A unique, air-foil shaped, padded cornering bar (or strut) emerged from the steering column, angled upward before transitioning into a horizontal component extending across the entire width of the interior.

To learn more about the 1956 Corvette Impala and other cars related to the GM Motorama get a copy of my new book, “Motorama: GM’s Legendary Show & Concept Cars.” Just click the book cover image at far right or click the link here: http://www.amazon.com/Motorama-Legendary-Show-Concept-Cartech/dp/1613251599/ref=pd_rhf_gw_p_img_1

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The LeSabre's styling was revised for 1953

1951 General Motors LeSabre: A Laboratory on Wheels

Full-size clay model of the 1951 GM LeSabre

     One of the earliest concept cars ever built was the 1951 GM LeSabre. (Note it was not a Buick but rather the General Motors LeSabre). Harley Earl, the first person ever appointed as vice president in charge of styling, headed the design of what was originally dubbed simply the XP-8. Within the GM Styling department a team was handpicked by Earl to handle the car's advanced styling. Engineering its mechanical systems was an even more ambitious matter.

     The structural aspects of the LeSabre were as radically different as the styling. Most of the body panels were of light-weight cast magnesium. Magnesium was being used in aviation applications like the first intercontinental range bomber, the massive Convair B-36; its use in an automotive application certainly added a flavor of the exotic to what was an astonishing car for the time. The front fender valence, cowl, door lock pillars, and deck lid were single large castings of magnesium. The remaining panels were of sheet aluminum. Ribs were cast into the deck lid to add strength to this large piece. Casting these members in magnesium was a difficult achievement; multiple attempts were required to get the correct shape for these components in order to get adjoining panels to align perfectly. When a panel was flawed, the magnesium was melted and recast again – even multiple times when needed. The floors were aluminum honeycomb sandwiched between aluminum sheets. Magnesium and extensive labor were partly responsible for the staggering price tag for this one-of-a-kind car which amounted to approximately $500 thousand or even as much as $1 million (which is today roughly the equivalent of $5 million and $10 million.)

LeSabre's supercharged, all-aluminum V-8

The complex body with stiff sills and driveshaft tunnel was set upon a ladder-type frame made of chrome-moly steel; wheelbase measured 115 inches. The parallel wishbone front suspension was atypical, too. Its A-arms were cast alloy with the upper A-arm pivot rod being imbedded in a solid piece of cylindrically shaped rubber which itself was encased in a steel casting. Hydraulic tubular shock absorbers were attached to the steel casings and the lower A-arms. With the rubber in torsion, it acted as an effective springing medium – at least for a while. Eventually, the rubber began to lose its elasticity resulting in Chayne replacing the setup with torsion bars. The rear of the chassis received a transaxle comprised of a modified Buick Dynaflow with a DeDion differential attached to it. (Some years later a four-speed Hydra-Matic replaced the Dynaflow.) The DeDion setup is a type of semi-independent suspension with a drop-center beam axle connecting the two driving wheels aft of the open, double-jointed drive shafts; it is separate from the final drive unit which is attached to the frame. A transaxle combines the final drive unit with the transmission which is located between the driving wheels; it separates the transmission from the engine, thus moving a significant portion of the weight towards the rear to provide improved weight distribution in rear-wheel drive cars. The rear-mounted torque converter was driven at engine speed which made possible the installation of a generator and hydraulic pump in the rear of the chassis. Each was driven by the input shaft of the transaxle. The hydraulic pump operated four built-in jacks (one at each corner) to raise the car when needed (i.e., changing a flat tire). The double-jointed axle shafts were made of magnesium and the rear suspension was a tapered single leaf spring mounted transversely. Thirteen-inch wheels helped make the car low, but to get adequate braking, 3 ½-inch wide, 9-inch diameter finned brake drums with four brake shoes per drum were used. The overall height with the top up measured just 50 inches; the cowl height as measured from the ground peaked at a mere 36.25 inches.

The engine was yet another amazing piece of engineering for the day. It was an experimental V8 with aluminum block and heads displacing 215 cubic inches – a volume obtained with a square bore and stroke (3.25 x3.25 inches). The block extended below the crankshaft centerline; its main caps were cross-bolted. Wet cylinder liners were centrifugally cast of Ni-Resist iron. Problematic at first was the intake manifold design. Before the actual engine was constructed, a mockup was made and sent to GM Styling. Joseph Turlay, who was in charge of engineering the special V8, was told by Harley Earl to make the engine at least six inches lower. Turley’s initial thought was that his boss’s order was impossible to accomplish. However, with some ingenuity he did it. He reduced the height of the oil pan and added a windage tray to keep the crank throws from aerating the oil. The flywheel size was reduced without sacrificing the mass required by substituting bronze in place of iron; this alone reduced engine height by 1 ½ inches. A Roots-type supercharger was neatly packaged just above the intake manifold which served as the valley cover. The chain driven camshaft was suspended from the bottom of the intake. Combustion chambers were hemispherical with the intake and sodium-filled exhaust valves mounted at a 90-degree angle to each other. The intake rocker arms were mounted transversely on the engine, while the exhaust rockers pointed fore and aft. This unusual arrangement allowed for a more compact engine to fit within the limited space of the engine compartment. Valve seats were stainless steel inserts.

There were even more mechanical marvels to the LeSabre. The oval grille in front as stated earlier is not really a grille, but rather a door which hides and supports close-set headlights. When the headlight switch was set to “on” the door moved inward, rotated 180 degrees, and then moved outward with both headlights aglow.

Rare color catalog detailing the interior of the LeSabre

Instrumentation for the LeSabre was extensive and its upholstery was of leather.... For more on the LeSabre purchase a copy of the author's book, "Motorama: GM's Legendary Show & Concept Cars," available for pre-orders at Amazon.com (release date is January 15, 2015). Motorama: GM's Legendary Show & Concept Cars

1954 Cutlass

A Radically Different Oldsmobile

     The 1954 Oldsmobile Cutlass made its public debut at the opening venue of the GM Motorama, the Waldorf-Astoria, in January 1954. While being designed at GM Styling under Art Ross, the car was known simply as the "long wheelbase F-88" and it shared some common features of the other Olds dream car, the F-88. Both were two-passenger cars with a similar instrument panel and powered by a modified 324 "Rocket" V-8 producing 250 horsepower. Wheels and some suspension components were also alike. However, as the name "long wheelbase F-88" implied, the Cutlass was a longer car. It was also a closed car with an unusual roof design ending in a tapering fastback with a louvered rear window. Up front was a divided oval-shaped bumper/grille combination with a set of driving lamps. The fiberglass body of the Cutlass was painted iridescent copper metallic, a special color developed for this dream car.
     Inside the Cutlass was a set of bucket-styled seats covered in pigskin; the seats swiveled to help ease entry and egress for the driver and passenger. There was no trunk lid, but access to the trunk was through a pass-through in the bulkhead behind the seats.
     Unlike some of GM's dream cars of this era, the Cutlass was made operable, and in fact, had a Michigan license plate attached.

     What became of the Cutlass after its days as a show car came to an end is not known, though there was a claim made many years ago it was actually sold to someone in the northeast. If true, where is the unique car today?

For more on the LeSabre purchase a copy of the author's book, "Motorama: GM's Legendary Show & Concept Cars," available for pre-orders at Amazon.com (release date is January 15, 2015). Click the book cover pictured at right to go directly there.