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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 car 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

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Illustrated Corvette Series No. 72 - 1986 Indy Corvette Concept Car
"Designing the Next Vette"

The lead time needed to design a car can be considerable. Many times, designers start the next generation of a design shortly after a new design is released for production. This was the case with the Corvette Indy concept car. With rave reviews coming in for the new C4 Corvette, it was time to think ahead – way ahead.

In the early '80s, Chevrolet engineers worked on a 2.65-liter Indy car engine with twin intercooled turbos. The engine was never seriously raced, but its development stimulated many of the Corvette team designers. Also, computer chips and electronics were making in-roads in production cars. GM's Design Vice President, Chuck Jordan, wanted these new technologies to be integrated into the design of the next-generation Corvette.

Jordan began with a rendering from staff designer Tom Peters. The design hearkened back to the Italian-like shapes from the Bill Mitchell era. Jordan took the Peters rendering and stuffed as much technology as he could into the sleek new shape.

The "Indy" name was used because the new car would have a 5.7-liter, 32-valve street version of the Indy-car racing engine. Corvette prototypes have had a long history of using mid-engine layouts, and the Corvette Indy was no exception. Other proposed "gee-whiz" features included active suspension, drive-by-wire steering, all-wheel drive, ETAK navigation system, and four-wheel steering.

To take the rendering to the next stage, Jordan commissioned Cecomp of Italy to build a full-size clay model of the Chevrolet III studio design. At this point, the high-tech specifications were just ideas on paper. It was the 3-dimensional, full-size model that would take the design to the next level of a running prototype.

The overall shape of the Corvette Indy was bigger than a production Corvette in every way except the height. The Corvette Indy was 7 inches shorter than a stock Corvette, but 10.4 inches longer and 8 inches wider. The wheelbase was 1.7 inches longer, with the front track 4.5 inches wider and rear track 5.4 inches wider that a stock Corvette. When viewed by it's self, the car looks large. However, when looked at next to a production Corvette, it looks very small due to its low height. The mid-engine drivetrain layout mandates a cab-forward shape. Deep air intakes behind the doors and the inverted rear spoiler are similar to many LeMans-type racers of that time. The upper rear spoiler shape would later be used on the '93 Camaro.

Clay prototypes are usually about 25 percent too much and have to be scaled back. The Corvette Indy successfully impressed GM officials, because by the end of '86 the first of two running Corvette Indy cars was delivered, with the second car being completed in '87. The running prototypes then became the starting point for the 1990 CERV III engineering study. - K. Scott Teeters

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lllustrated Corvette Series No. 76 - 1988 Running Indy Corvette
"The Running Prototype"

After seeing the full-size Corvette Indy clay model, GM brass approved the construction of a running prototype of the bold new design. Clay models are always a little over the top and need to be pulled back, but the running Corvette Indy still sizzled.

The second-stage Corvette Indy was a three part project. The overall design shape and hardware specifications came from the Corvette design team. Since GM had recently purchased Lotus, it was decided to use Lotus' suspension engineering skills to develop a prototype active suspension system. And finally, Cecomp of Italy was contracted to assemble the finished running vehicle. This was to be an interim car while the CERV III engineering study was being built.

Dream cars can be very exciting, but are often not road worthy as production cars. So the original design had to be more realistic. The front end was shortened and the A- and B-pillars were a little more realistic. Also, extra ground clearance and wheel travel in the wheel openings was added. But the shape, flavor, style, and attitude remained.

Running gear was as cutting edge as could be. An early version of the 5.7 LT5 (ZR-1) engine was used. Placement was not only mid-engine (something that Duntov wanted for decades), but was also transverse mounted. The backbone chassis was made of carbon fiber rather than the Kevlar tub of the first version. The Lotus team got to show off their latest active suspension hardware that had just about everything you could imagine. Micro processors and hydraulics replaced the entire standard suspension. The car had full-time four- wheel-drive, four-wheel steering, ABS brakes and traction control. The active suspension allowed for smaller wheel houses, fewer parts, and more interior room.

Weighing only 3,300 pounds and packing 380 hp, the Corvette Indy had enough grunt to carry the Corvette flame. The next stage would be the production-like CERV III. As a prototype, the running Corvette Indy was a success! - K. Scott Teeters

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lllustrated Corvette Series No. 84 1990 CERV III
"Over the Top Design"

The CERV III was a real-world version of the Corvette Indy show car. The Corporate Engineering Research Vehicle III (CERV III) was more than pretty show car; it would be the most advanced Corvette study to date.

Chief of Chevy III Studio, Jerry Palmer, handled the styling details while Dick Balsey was the engineer on the project. The objective was to showcase the Chevrolet design team and Lotus' advanced racing experience. This was no easy task, by any means.

The nose of the Indy had to be shortened and the side windows flattened out so that they could go down into the doors. The wheel openings had to be opened up to allow 3.5 inches of travel and the rocker panels reshaped to accommodate side-mounted fuel cells. Also, the overall height had to be increased a few inches.

The CERV III's hardware was just as exciting as the body shape. To start, the LT5 engine was treated to two Garrett T3 turbochargers that bumped the horsepower up to 650 and the torque to 655 lb-ft. The 3,400-pound CERV III ran 0 to 60 in 3.9 seconds, had a top speed of 225 mph, and had 1.1 gs of lateral acceleration!

Since the car was completely built by Lotus in England, carbon fiber was used everywhere possible, just like a race car. The underbody was carbon fiber with a fiberglass-finish coating. The classic Lotus backbone chassis was made of carbon fiber and weighed only 38 pounds.

Although the suspension looked normal, the springs and A-arms were made of titanium. Actuators were used in place of shock absorbers and were connected to a state-of-the-art computer-controlled active suspension system. ABS braking and traction control was also part of the package. The transverse-mounted engine used a six-speed automatic transmission for all-wheel-drive and four-wheel steering.

The completed car was more than anyone expected, especially the bean counters. Cost estimates put the price tag between $300,000 and $400,000, making the world-class CERV III the most expensive proposed Corvette ever! - K. Scott Teeters

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lllustrated Corvette Series No. 90 - 1991 ZR2 Engineering Study
"Chevrolet's Big Doggie!"

Some Corvette engineers have all the fun. In the mid-'80s, Scott Leon was a Corvette Project Coordinator at the GM Proving ground in Arizona. Although the new C4 Corvette was a success, there were those that missed the old big-block Corvette power. But Scott Leon had a plan.

One night after work, Leon and his crew decided to see if a big-block engine would fit into the frame rails of a C4 Corvette. Using an old '84 mule Corvette, the crew was surprised to find that with only a few chassis modifications, the big rat motor fit into the Corvette. The engine was a real squeeze, but it worked. Leon wanted the car to be modern, so they cobbled together a tuned-port fuel injection unit with a modified aftermarket tunnel-ram intake manifold. With a little welding and a set of Buick Grand National injectors, the system worked.

The crude engineering study was enough for Leon to get management to agree to building a 454 prototype using a '86 Corvette Coupe with an automatic transmission. Later, another prototype was made using a '89 Roadster with a 6-speed transmission and a Z51 suspension. Now things were starting to get real interesting.

The final version of Big Doggie was a very impressive machine. Leon chose one of Chevy's marine 454 short-block and added a set of L88 aluminum heads. The engine assembly was modified so that all production accessories would bolt on. The only modifications to the car was to the floor pan and the right side of the frame rail, forward of the fire wall. Aside from the large raised hood, the package looked like a production car.Even under the hood, everything looks like it came off the assembly line.

The ZR-2's 454 engine was never dyno tested, but was estimated at 385 horsepower about the same as a ZR-1, but with a big difference. Big Doggie had much more low-end torque than a ZR-1 and pulled like a freight train. With the Z51 suspension parts and a 6-speed transmission, the car was a hoot to drive. To save weight, Leon used the optional hard top and removed the convertible mechanism.

Big Doggie's chances of it ever seeing its way into production was close to zero. Chevrolet had too many of its eggs in the ZR-1 basket and the big-block engine didn't meet federal fuel standards. For a time, there was talk of offering a retro kit. But ZR-1 performance at a fraction of the cost wasn't what GM was interested in. - K. Scott Teeters

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Illustrated Corvette Series No. 93 - 1992 Falconer V-12 Experimental Corvette
"The Conan Corvette"

When the Dodge Viper debuted at the North American International Auto Show in January 1989, NO ONE knew what hit them. The Viper was new and fresh, yet it had a definite connection to the Shelby Cobra. Advanced orders were flooding in you know that designers were going back to the office saying, "DAMN!"

The Corvette team was working on three fronts: improving the production Corvette, getting the LT-5 (ZR-1) ready for production, and honing the CERV III prototype as a possible C5 Corvette. But the economy wasn't good and the reality of a CERV III-based car seemed dim at best Meanwhile, Chrysler was going into production with the V10-powered Viper. This posed a serious threat to the Corvette's "America's Only True Sports Car" status.

Under the guise of a "chassis development" program, the Corvette team came up with the idea of trumping the V10 Viper with a V12 Corvette prototype. Enter Ryan Falconer.

Falconer got his start in the early '60 working for Andy Granatelli's Novi engine -powered Indy racers. Later he joined in the Shelby American team and worked on the GT40 and racing Cobras. Two years later, Ryan started his own company, building his own racing engines. His associates reads like a "who's who" of auto racing legends, including; Parnelli Jones, Al Unser, Mario Andretti, Jackie Stewart, and many others.

So when the Corvette team decided to one-up the Viper with two extra cylinders, they decided on one of Ryan Falconer's stunning, all aluminum V12 racing engines. Since the Corvette would have to be stretched, this was the perfect time for a "chassis study."

Since the Falconer V12 packed a 680-horsepower kick, the obvious place to begin was with a production ZR-1. The biggest challenge was the fact that the all-aluminum V12 engine was 8.8-inches longer than the production Corvette engine. So the front end of the ZR-1 would have to be stretched 8-inches. SportsFab of Wixom, Michigan was contracted to do the stretching. The extra length is barely noticeable, but the '60s-styled side pipes sure are. Those were straight-through pipes directly off the tuned headers with no mufflers! With the hood up, the engine looked enormous. Amazingly, the extra length and the larger engine only added 100-pounds to the overall weight of the car. The engine used electronic fuel injection with a short-runner intake manifold and the aluminum block had pressed in cast iron sleeves, similar to the famous ZL-1

Actual performance figures were never published, as this was just a "chassis study." But you can figure out the power-to-weight ratio. What was certain was that at $45,000 per engine, plus the chassis and body modifications, there was no chance this car would ever get into production. Nick-named "Conan" because of the huge V12 engine, the ZR-12 was without a doubt, the one of the baddest engineering study Corvettes ever made. - K. Scott Teeters