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Illustrated Corvette Series No. 50 - 1973 Corvette
It was not a good time to be a Corvette, and Zora Arkus-Duntov clearly saw that speed, power, and performance were obviously "out." So Duntov set out to make his Corvette the best he could. In 1972, while showing one of his mid-engine prototypes, a GM board member commented, "What do you want a new car for? You're selling all you can right now!"
That's like saying, "If it ain't broke, don't fix it!" But you can make it better. Duntov wanted to use his final years at General Motors to make the Corvette a quality automobile. The demand for the new C3 Corvette was so high that extra production shifts were added and quality seriously suffered. By '72 "quality" was the least-liked feature of the Corvette. Customers didn't like the Cadillac price with a Vega finish. Thus, Duntov began polishing the '73 Corvette to meet new performance standards.
Corvette sales had been rising since 1972, and continued so until 1978. Although serious cars guys bemoaned the lackluster power and soft touches, Corvettes were more popular than ever. The bean-counters were very happy. The most obvious change for '73 was the new front bumper and hood. All cars now had to have 5 mph crash-bumpers. The new hood featured a cowl- induction system, and eliminated the troublesome "wiper closet" from earlier C3s. The doors now had guard-beams for added safety. Extra sound-deadening material was added as well as rubber body mounts to make the car quieter inside. GR70x15 radial tires also helped ride quality.
In 1973, only three engines were available: the base 190 horsepower 350, the $299 L82 350 with 275 horsepower, and the $250 LS4 454 with 275 horsepower. Solid-lifter engines were no longer available.
Despite the added weight and the soft touches, buyers didn't care. In 1973 30,464 Corvettes were sold. Duntov spent '68 to '72 making the C3 a rip-snort'n pavement burner. His final efforts actually saved the car in the '70s. Thanks Zora! - K. Scott Teeters
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lllustrated Corvette Series No. 51 - 1973 XP-892 Mid-Engine 2-Rotor Experimental Corvette "Rotor-Motor Wankel Corvette?"
The XP-892 just flat-out caught everyone short. It didn't "look" like a Corvette, and used an engine that most of us had never heard of. "What's a Wankel?" Despite its unusual styling, it was a very well done prototype. However, due to the Corvette's sales success, GM was in no hurry to make an all-new car.
GM was hot on the new Wankel rotary engine, and was scheduled to offer the rotor-motor in the Vega for '75. Since 1953, people inside of GM have wanted to make the Corvette something else smaller, bigger, a four-seater, etc. So a Wankel powered prototype was ordered. Actually, two prototypes were made, the XP-892 two-rotor design, shown here, and a four-rotor design using the chassis from the '70, mid-engine, V-8 powered XP-882.
The XP-892 was small, about the same size as a Dino Ferrari or a Datsun 240Z. But when pressed for inside information as to the possibility of this being the next Corvette, the ever cagey Duntov was quoted as saying, "Maybe, but there are no plans to produce it."
The problem was that at 2,600 pounds, with only 180 to 250-hp, performance wouldn't be anywhere close to Corvette standards. Since the Wankel engine had serious heat problems, the XP-892 was more of a study to see if the engine was feasible for a small sports car. Power-to-weight ratio aside, everyone was very pleased with the way the car turned out.
The XP-892 was designed by Chevrolet and built by Pininfarina. Unlike a production Corvette, the XP-892 was a steel, unit-body construction. Duntov referred to the McPherson-strut, independent suspension, and disc brakes as "run of the mill." The 266 cid engine had a single Rochester four-barrel carburetor, and was mated to a modified Hydramatic transmission. Duntov clearly wanted more when he said, "Add three more inches of wheelbase... and maybe a 300-cid engine, and we'd have a good car." As always, he had "something else" up his sleeve, a larger, four-rotor version.
For a prototype, the XP-892 had a very well designed and finished interior. The seats were fixed while the seat backs, steering wheel, and pedals were all adjustable. Between the engine and interior there was a 8.1 cubic foot storage space. The spare tire was under the front hood. It seems that the press never drove the car, as there was never a mention of how the car performed.
GM privately showed the XP-892 and the V-8 powered XP-882 to potential Corvette buyers in '72. The test groups wanted to see something in between. Duntov's opinion was, "When we finally decide what the new Corvette will be, it will be for our own reasons." The man knew what he wanted. - K. Scott Teeters
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lIlustrated Corvette Series No. 52 - 1973 Mid-Engine 4-Rotor Experimental Corvette
"148-MPH Prototype Corvette!"
Zora Arkus-Duntov had that rare blend of a deep understanding of engineering and a passion for speed. Aesthetics did little for Duntov, unless it helped the car's performance. Concerning the Four-Rotor Corvette, Duntov was quoted, "Looking back on my 20-year association with styling, this is the best design ever produced."
From '68 to '73, Chevrolet R&D made five unique mid-engine prototypes. So, what happened? The mid-engine Corvette dream never made it into production because of the Corvette's sales success in the early '70s. Production was at an all-time high in '73, and Chevrolet returned 8,200 orders to dealers because they couldn't make enough cars! So, strictly from a business standpoint, "We're selling all we can make, don't change it!"
Another interesting situation was going on inside of Chevrolet. Four power-players were approaching the end of their careers, and they all wanted a spectacular replacement for the Corvette. Duntov from engineering, Bill Mitchell from styling, Joe Pike from sales, and GM President Ed Cole were powerful Corvette allies. But in business, the bottom line is king.
The 2-Rotor car was nice, but more power was obviously needed. So a bold plan was presented to get the job done. Using the chassis from one of the '70 XP882 cars, two 292.5-cid rotary engines joined together inside a stress member case. The 585-cid "engine" made close to 420hp. The transmission was a Turbo Hydramatic 425 from a Toranado, with a Morse Hy-Vo chain and bevel gears.
Styling was directed by Mitchell and penned out by Henry Haga. Starting with the bumper height datum line, Mitchell's instructions were to "make it sleek." The long tapers on the front and rear, and a steep windshield, made the drag coefficient only 0.325. Gull-wing doors, vents, louvers, scoops, and lots of show car trim made the 4-Rotor Corvette nearly perfect from every angle of view. Slightly longer, lower, and wider than a production '74 Corvette, it looked like "the future."
On a one-mile check track, GM president Ed Cole and Duntov clicked off 148 mph in the 4-rotor Corvette. The car started out with a throaty roar and hit top speed, belching flames and making an ear piercing scream. It was actually faster than a '73 454 Corvette! But not even powerful friends in high places could get this prototype into production. - K. Scott Teeters
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lllustrated Corvette Series No. 53 - 1973 XP-895 All-Aluminum Experimental Corvette
Despite the dark clouds on the automotive horizon in the early '70s, it was a heady time in the Corvette R&D group. The all-aluminum Corvette was the third fully functional prototype to show up in '73.
Before carbon fiber, aluminum was the darling of high-tech automotive development. After all, aluminum was the material of cutting-edge jet aircraft and space craft. An aluminum bodied car wasn't a new idea, since many European exotics had aluminum bodies, as well as Shelby's Cobra. But an aluminum "production" car is another matter.
Like aircraft and space craft, weight was the motivator for this feasibility study. Since the early '60s Detroit had been offering "off-road" aluminum parts intended for NASCAR and drag racing, but these were limited to bumpers, fenders, hoods, doors, and mounting hardware. Mass producing an entire car body would require many assembly and durability considerations. But the prospect of reducing body weight by 40 percent was very appealing.
Using the same chassis and basic body shape of the 2-Rotor Corvette prototype, Reynolds Aluminum used their new 2036-T4 allow to make this all-aluminum Corvette. Except for the bumpers, tires, and interior parts everything else is aluminum. Chevrolet supplied stress analysis and Reynolds sorted out everything else. The main constraint was that the body would have to be spot-welded like a production car. To compensate for aluminum's lower modulus of elasticity, many of the parts and attaching flanges had to be thicker. Two-part epoxy was also used for added strength and to eliminate crevices that would trap salts and dirt.
The Reynolds Aluminum Corvette had minor body differences from the 2-Rotor prototype and used a 400-cid small-block mated to a Hydro-Matic automatic transmission. Side-by-side, the Reynolds car weighed over 400 pounds less than the steel bodied 2-Rotor prototype. But weighed against the Corvette's sales success of the early '70s, GM was in no mood to make an aluminum Corvette. - K. Scott Teeters