Mid Engine Corvette History
Mid Engine Corvette History
Here’s a brief history of the experimental and developmental Corvettes and engineering exercises that have caught our eyes for the past six decades. I’ve personally been reading about possible mid engine Corvettes since the early 1970s. So here is the history:
1960 CERV I
Following a dismal DNF at the 1957 Sebring Grand Prix, Corvette patron saint Zora Arkus-Duntov concluded that the “heat source” (his expression for the engine) was in the wrong place. This prompted abandonment of the Corvette SS’s conventional front-engine, rear-drive layout in favor of a mid-engined open-wheel single-seater mimicking the day’s winning Formula 1 racers.
Duntov designed this Chevrolet Engineering Research Vehicle (CERV) around a small-block V-8 blessed with an aluminum block and heads and a few cast-magnesium parts. The first engine produced 353 horsepower, but trials with supercharging and turbocharging eventually kicked it over the 500-hp hurdle. Tests were conducted at Pikes Peak, Riverside, Sebring, and Daytona Beach. Duntov topped 200 mph in this car at GM’s Milford, Michigan, proving grounds.
The independent rear suspension developed here went straight into C2 Corvettes introduced for the 1963 model year. In 1972, GM temporarily lost control of the CERV’s fate by loaning it for display at the Briggs Cunningham museum. After it spent years in private hands, the company spent $1.3 million at a recent Barrett-Jackson auction to return the CERV to the fold.
1964 CERV II
Duntov’s racing itch was unrelenting. To exploit lessons learned from the single-seater and to thwart Ford’s international endurance-racing ambitions with the GT40, his next research vehicle was a more ambitious design. Moving the transmission from CERV I’s location—between the engine and the differential—improved mass distribution and shortened the wheelbase. To trim weight, the two-seat cockpit was a steel monocoque with the powertrain and a tubular spaceframe serving as stressed rear members. A 6.2-liter mostly aluminum SOHC small-block V-8 provided 545 horsepower.
CERV II’s masterstroke was a four-wheel-drive arrangement worthy of a U.S. patent. A compact two-speed automatic transaxle drove the rear wheels. To power the front axle, there was a driveshaft running from the crankshaft’s nose to a second automatic transaxle. Front torque was limited to 35 to 40 percent of the total twist by using a smaller torque converter at that end of the car.
CERV II ran 214 mph in testing (in 1970 with a 427 ZL1 engine transplant), but the program was halted in the fall of 1964 when GM management felt that the design concept was obsolete.
1968 XP-880 Astro II
An interesting situation that existed at General Motors in the 1960s was the freedom enjoyed by organizations outside the Corvette group to pursue alternative sports-car designs. Building on the Corvair’s layout, GM’s R&D staff hung a V-8 out the back of a stylish two-seat coupe, with predictable results: wildly uncontrollable limit handling.
To make amends and to counter Ford’s mid-engined Mach 2 concept car that had appeared at the 1967 Chicago auto show, R&D rejiggered that car, fitting a big-block V-8 ahead of the rear wheels. The resulting Astro II New York auto show car was flawed. It was wrapped in a meek envelope with no provision for headlamps, and its Pontiac Tempest two-speed transaxle lacked sufficient torque capacity. None of that stopped Road & Track from featuring this experimental sports car on its July 1968 cover, teasing readers with the suggestion that it was a street-legal Chaparral.
Continuing the cat-and-mouse competition with Ford, Duntov countered the launch of the DeTomaso Pantera (not to mention the Mercedes-Benz C111 and AMC’s AMX/3) at the 1970 New York auto show with his latest fantasy. This one, billed simply as a Corvette prototype, embodied another clever means of marrying a mid-mounted V-8 to four-wheel drive. This time, a 7.4-liter engine was bolted to an Oldsmobile Toronado transaxle and positioned transversely between the driver and the rear differential. A second output shaft ran forward to the front diff, and all the hardware fit neatly within a 95.5-inch wheelbase. Two shortcomings were a slightly elevated engine to accommodate the front driveshaft and no ready means of offering a manual transmission. Nonetheless, the arrangement earned Duntov another patent.
Road & Track bit the bait, declaring in its July 1970 issue, “We’ll stake our reputation on this being the Corvette of the future—but don’t expect it until 1972 at the earliest.” Unfortunately, GM’s management was less enthusiastic.
1972 XP-895 Reynolds Aluminum Corvette
After pondering a switch from fiberglass to steel bodies for the Corvette, with the inevitable conclusion that the weight gained vastly exceeded the cost savings, GM boss John DeLorean convinced Reynolds Metals to craft a unibody Corvette in aluminum. Both the steel XP-892 and the visually identical aluminum XP-895 were production-intent mid-engine designs.
The net weight savings was 500 pounds. The panel joining technology—spot welding combined with epoxy adhesives—migrated throughout GM. Unfortunately, the cost of switching from fiberglass to aluminum bodywork was a showstopper.
During GM’s anything-goes era, it came close to building and selling Wankel-engined cars. The compact rotary would have been a boon to tightly packaged sports cars.
Using the Dino 246GT as a role model, GM’s design staff created a tidy yet attractive two-seater with a two-rotor engine positioned transversely behind the driver. To save time, Pininfarina was contracted to build the necessary body panels, and most of the chassis came from a Porsche 914.
Upper management was impressed by how quickly the design team built a running car, rewarding the effort by granting an appearance at the 1973 Frankfurt auto show. In spite of a generally favorable reception, this mid-engined Corvette sank with GM’s rotary.
Two rotors whirling out 180 horsepower were not nearly enough for Duntov. So, concurrently with the XP-987GT, he lashed together two GM Wankel engines for a revived XP-882, known to its admirers as the Four Rotor Corvette.
Bill Mitchell, Jerry Palmer, and their able assistants freshened the Corvette prototype’s skin with radically pointy ends, folding gullwing doors, and a creased windshield laid back 72 degrees from vertical. The interior featured an early application of digital display technology with 29 LEDs reporting engine rpm.
Duntov treasured a scale model of the Four Rotor at his home, rating it the aesthetic equal to his all-time favorite Corvette, the 1957 SS (ironically, the car that prompted the engine’s rearward migration). Recently retired GM design boss Ed Welburn concurred, referring to the Four Rotor as one of the General’s crown jewels.
The two rotary Corvettes shared a stand at the 1973 Paris auto show. Four years later, GM announced the demise of its rotary-engine research. The total cost was an estimated $50 billion.
Fortunately, both of the mid-engined Corvettes lived on. The 2-Rotor is owned and displayed by a Corvette specialist in Snodland, England. The 4-Rotor’s reprieve was a conversion to conventional V-8 power. Rechristened Aerovette, this mid-engined Corvette now resides at GM’s Heritage Center.
1986 Indy/CERV III
Following the C4’s launch in 1983, the first major overhaul for the Corvette’s chassis in 20 years, GM Design maintained its mid-engine mindset for possible C5 use well after Duntov had retired.
Designed in-house, modeled in Italy, and given life by Lotus in England (then owned by GM), the Corvette Indy contained every known tech tidbit except a kitchen sink: active suspension, all-wheel drive, four-wheel steering, drive-by-wire, and the newest navigation and cockpit display gear. The name was inspired by the twin-turbo 4.3-liter V-8 Chevy supplied to Indy racers.
Significantly longer, wider, and lower than the day’s production Corvette, the Indy boasted a composite chassis and a transverse engine orientation. CERV III—now standing for Corporate Engineering Research Vehicle—followed at the 1990 Detroit auto show with the engine swapped to a twin-turbo, 650-hp version of the Lotus-designed 5.7-liter DOHC V-8 (the original LT5).
2002 Cadillac Cien
This is obviously not a Corvette, but GM celebrated Cadillac’s centennial and affirmed its devotion to the mid-engine layout with this magnificent show car, allegedly inspired by the F-22 Raptor stealth fighter.
The Cien bowed at the 2002 Detroit auto show. The experimental 7.5-liter V-12 behind the cockpit was rated at a potent 750 horsepower and previewed both direct fuel injection and displacement on demand. Following Simon Cox’s design effort in GM’s London studio, England’s Prodrive engineering shop advanced the effort to the running-prototype stage. The body and chassis were made of an ultralight material called Aerogel.
2006–2008 C7 Engineering Proposal
Instead of adopting a mid-engine layout for the sixth-generation Corvette, introduced in 2005, engineers focused on enhancing performance with better handling and additional power. The Z06 version packed 505 horses into a 7.0-liter small-block. Topping the 6.2-liter V-8 with a supercharger yielded the 638-hp ZR1. A cost-effective Grand Sport brought comprehensive suspension and brake upgrades.
These achievements did not hinder assistant chief engineer Tadge Juechter from championing the move to mid-engine just like his predecessors. GM designers played along with a full-size clay and more than a dozen scale-model alternatives. (The image here was created by C/D’s own Cory Wolfe, not GM.) Tom Wallace, Juechter’s boss and an inveterate road racer, was an easy sell. GM product chief Bob Lutz was initially skeptical but became convinced by the Juechter-Wallace tag team. The three mid-engine musketeers then won over chairman Rick Wagoner.
Unfortunately, GM was bleeding cash, and it slipped into bankruptcy when the Great Recession hit in 2009. The mid-engined Corvette—along with every dollar aimed at developing any new sports car—left the building with Wagoner. When the feds arrived to revive GM, an early discovery was the fat profits associated with selling 30,000 or so Corvettes per year. Work on the seventh generation quickly resumed, but the time was not right to risk the mid-engine move.
Fortunately, C7 has helped GM thrive, and the planets have finally swung into alignment. Just as Road & Track did in 1970, we’ll stake our reputation on the mid-engined C8 Corvette arriving before the end of 2018.
By Don Sherman | Illustration by Cory Wolfe