The Rear-Engine Corvette That Was Never to Be

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ON Sunday evening, just ahead of two press preview days for the 2013 North American International Auto Show in Detroit, Chevrolet will unveil the seventh generation of the Corvette. While the two-seat sports car accounts for a small fraction of Chevy's total sales, it is a vital element of the brand's image -- and, in fact, its longest-running passenger-car nameplate.

The debut of the redesigned 2014 model, known among the Corvette faithful as the C7 and set to go on sale in the fall, will answer questions that have swirled around enthusiasts' online forums for years. Among the unknowns to be resolved is the car's basic layout: will the engine be in the front as it has been for 60 years (most likely), or will it at last be positioned behind the passenger compartment (quite doubtful), as many fans of exotic sports cars have long felt it needed to be?

As details of the new car are being revealed in Detroit, some 600 miles to the east a storied Corvette engineering prototype will be progressing toward the final phases of a restoration. The XP-819, a one-of-a-kind research vehicle developed by General Motors engineers in the 1960s, is one of the cars that has given rise to recurring rumors that each new generation of Corvette may be the breakthrough model elevating the Chevy to supercar status. Long out of sight after a crash during testing, the XP-819 is being brought back to life at the Long Island shop of Kevin Mackay.

"We have over 3,500 hours into the restoration to date," said Mr. Mackay, whose Corvette Repair in Valley Stream, N.Y., has revived significant Corvettes like the Briggs Cunningham team racecar that won its class at Le Mans in 1960 and the 1963 Corvette Coupe Speciale Rondine, a one-off Pininfarina-designed show car.

"This is a one-of-a-kind vehicle," Mr. Mackay said of the XP-819. "So unlike a regular Corvette, most of the parts on this vehicle have to be handmade. This is by far the most challenging project we have ever worked on."

Mike Yager, founder of Mid America Motorworks, a Corvette and VW parts and accessories supplier based in Effingham, Ill., bought the XP-819 at a Monterey, Calif., auction in August 2002.

"The original focus of my collection was on low-mileage, highly original Corvettes," Mr. Yager said.

But Mr. Yager didn't like it when people who saw his collection said they had seen cars like his before, he said. So he decided that one-off cars -- experimental cars and design concepts -- would be the focus of the collection.

The singular XP-819, a rear-engine design, certainly meets that standard. And beyond its daring mechanical layout, the car's racy silhouette, from the design studio of Larry Shinoda, previewed styling elements seen in the 1965 Mako Shark II concept and served as a major influence on the third-generation Corvette that made its debut in 1968.

Chevrolet has released only engine specifications for the 2014 car. The rumors of a midengine design -- repeatedly denied by General Motors -- seem unfounded once again, as they have proved throughout Corvette's rich history. From what is known, the C7 is decidedly evolutionary, using advanced technologies like direct fuel injection but maintaining the basic pushrod design of the small-block V-8

Still, G.M. built, tested and, in some cases, displayed at public shows more than a dozen experimental prototypes that featured mid- or rear-engine layouts from 1958 to 1973. The period was a long, dreamy exploration into advanced sports car design and reflected the optimism of the times.

"This was the golden era of G.M., where because of their market share and incredible profits, they had the resources to create these skunk works," said Jerry Burton, a Corvette historian, referring to various development efforts within G.M.

Despite all of the noteworthy innovations and forward-looking design cues that came out of these experimental vehicles, Corvette has retained the same basic front-engine V-8 layout.

"The design staff was really calling the shots back then," Mr. Burton said, noting the fondness for the long-hood look held by the vice president of styling, William L. Mitchell.

Zora Arkus-Duntov, the engineer most closely associated with the Corvette's early years (though he did not become the car's official chief engineer until 1968) had long wanted to build a rear-engine development car, according to members of the engineering staff in that period. After all, Porsche and VW had made rear-engine layouts work and, as Duntov saw it, a rear-engine Corvette came closer to the purist midengine layout he craved in a sports car without incurring the problems of engine cooling, passenger space and crashworthiness.

Duntov provided basic mechanical specifications for coming research cars but did not have direct involvement in the XP-819 design. That was the responsibility of Frank Winchell, a top engineer who had worked on rear-engine sports-racing cars and the Corvair production model.

"Zora and Winchell were big rivals," said Mr. Burton, who wrote a biography of Duntov (Bentley Publishers, 2002). "Winchell was introverted and quiet. Zora was a showman who resented not being more involved. He felt that anything to do with Corvettes should be under his control."

For legal reasons relating to the Corvair lawsuits that were starting to appear and the handling challenges that arose when rear-engine vehicles were pushed to the limit, those who worked on the XP-819 knew that mounting the engine behind the rear axle, rather than in the middle of the car, was not necessarily the best plan. Instead, they viewed the project as a way to learn more about optimal engine placement.

One of the things engineers did to compensate for the vehicle's 69 percent rear weight bias was to run the gas tank -- a flexible urethane bag instead of a traditional steel fuel tank -- through the large central backbone that formed the main section of the chassis.

"The car was a test bed for technology," Mr. Mackay said, pointing out features the XP-819 previewed, like adjustable pedals, a one-piece removable roof and urethane foam bumpers that distributed impact loads through the fiberglass skin to the chassis.

Paul Van Valkenburgh was a young aerodynamicist hired by Winchell in 1965 because of his experience building scale-model wind tunnels. As a G.M. staff engineer who had a hand in the XP-819's creation, he held a great fondness for the car.

"It was one of the most beautiful shapes I had ever seen," Mr. Van Valkenburgh said, in contrast to the view held by Duntov, who had named the XP-819 the ugly duckling. "I walked past it every working day for two years and would have taken a second mortgage on my house to buy it at the time."

"I did have negative comments about the handling after driving it, but I wasn't a development driver and wasn't tasked with pushing it to the limit," said Mr. Van Valkenburgh, who went on to publish several auto racing books after he left G.M. "We all realized the fundamental physics of a car like that."

The car did eventually spin out one day at G.M.'s proving grounds in Milford, Mich., while doing a double lane change test, ripping the front end off. The car was repaired after the crash for continued testing, but Chevrolet decided not to continue development as a production vehicle -- or to keep it around for history's sake.

William S. Knudsen, the head of Chevrolet at the time, sent the car to the shop in Daytona Beach, Fla., of Smokey Yunick, the legendary engine expert and stock car builder, with instructions to chop it up. As happened with many experimental vehicles and concept cars that came out of G.M. in those days, Yunick didn't dispose of the car as instructed.

The remains of the XP-819 were left in one concentrated huddle in a paint booth inside the shop. Years later, a Chevrolet dealer named Steve Tate recognized the unique XP serial number in the parts pile and promptly bought the car from Yunick, eventually reassembling it. The car changed owners a number of times and was displayed at the National Corvette Museum in Bowling Green, Ky., for several years.

"We discovered the car was put together very crudely, after taking delivery," Mr. Mackay said. "It was a diamond in the rough. The entire center section of the frame was missing. We rebuilt the chassis and reskinned the car by grinding the body down and adding layers and layers of fiberglass."

A drivable chassis -- sans body, but with functional brakes, steering column and two seats -- will be prepared and driven onto the Amelia Island Concours d'Élégance show field in March. The plan is that the XP-819 will be shown as a finished car, body and all, next year at the same show.

"When I think about 819, I know that I will be able to confidently tell people who visit my museum, 'You have definitely never seen one of these before," ' Mr. Yager said.

autonews

This article originally appeared in The New York Times.


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