King of the Hill
As the C4 was making its debut, Corvette engineers and product planners were looking down the road at ways to keep the Vette the top-of-the-heap halo vehicle Chevrolet needed it to be. It was feared the incremental power gains squeezed from the L98 weren't going to be enough to fend off foreign competition.
So McLellan put Chevy's powertrain people to work. Early experiments at turbocharging didn't pan out, but the engineers were encouraged by the potential offered by overhead camshafts and multiple valves in the heads. Following this path led to an arrangement with Lotus, with which GM designed an all-aluminum, 32-valve, dual-overhead-cam V-8. Once the design work was completed to Chevy's satisfaction, manufacturing of the engine was turned over to Mercury Marine in Stillwater, Oklahoma.
The overhead-cam design made for a small-block with a wholly different character, a high-winding motor that didn't hit its 375hp peak until 6,000 rpm. McLellan knew putting all that power to the ground meant installing fatter rear tires, which would also necessitate wider rear-end bodywork. To further set off this new super Vette, the car's round taillights were squared off.
The engine was named the LT5, and early prototypes of the Vette had an LT5 badge under the passenger-side taillights. GM brass didn't want to use the engine's RPO code that way, though, so production versions were badged with the car's official name. Though early in its development Chevrolet Chief Engineer Don Runkle called it the "King of the Hill," the company went back in time to revive a high-performance RPO number from the early '70s: ZR-1.
Journalists first tested the car in Europe after its debut at the Geneva Auto Show in 1989. Though it was intended to be an '89 model, by the time all the engineering was sorted out, the corporation tagged the cars as '90 models.
The ZR-1 was an incredible performance machine. Motor Trend clocked the car at 4.75 seconds from 0-60 and 13.13 seconds through the quarter-mile, while the hot shoes at Car and Driver dipped into the high 12s. Yet the ZR-1 RPO carried an equally stratospheric price tag: $27,000 over the $32,000 cost of a '90 coupe to base it on. Despite that steep sticker, some 3,000 ZR-1s were sold in '90.
All told, the ZR-1 option was available from 1990 to 1995, and the car saw minimal changes during those years. Output rose to 405 hp in '93, the same year Corvette celebrated its 40th anniversary. That was also the year Mercury Marine stopped making the LT5 engine, leaving enough of a surplus to continue building the car in limited numbers for two more years.
Closing the Gap
There were several reasons for the ZR-1's short life. A stagnant economy made it hard for Chevrolet to find buyers who would pay the car's steep price, and getting the LT5 to pass the stricter emissions standards for the upcoming '96 model year would have been prohibitively expensive.
Plus, the standard Corvette was going through a series of upgrades that closed the gap between it and its supercar brother. First came a new look: All Corvettes received the ZR-1's squared taillights in '91, in addition to a revised front fascia, new fender louvers, a new turbine-style wheel design, and the Z07 adjustable suspension package, which replaced the Z51 option. Then in '92 the L98 small-block V-8 was replaced by the first of the Gen II small-blocks. The new 350-inch motor, named LT1 after the LT-1s from the '70s, was good for 300 hp--a significant increase.
Another milestone passed in 1992, as Dave McLellan retired and handed his Chief Engineer job to David Hill. Hill had come from Cadillac, but he had extensive personal experience with sports cars, both foreign and domestic.
That changeover happened just a year shy of the Corvette's 40th anniversary, which was commemorated in the '93 model year with a 40th anniversary package: Ruby Red Metallic paint (with leather upholstery to match), special emblems, and body-color wheel centers. Also new for the model year was the first keyless entry system.
The '94 model year saw several changes to the Vette's interior. Leather upholstery became standard (and cloth unavailable), the steering wheel and instrument panel were redesigned, and there was now an airbag in front of the passenger seat. Underhood the LT1 was fitted with a new sequential fuel-injection system that improved throttle response and lowered emissions, though output numbers remained the same.
Corvette paced the Indy 500 for the third time in 1995, and 527 pace-car replicas were built, each finished with the Indy car's distinctive purple-over-white paint scheme. Standard '95 Vettes received revised front fender louvers and softer springs, while the big front disc brakes that were part of the ZR-1 and Z07 packages became standard on all Vettes.
By 1996 the much-delayed fifth-generation Corvette was finally waiting in the wings, as was an all-new small-block V-8. Chevy marked the end of the C4 era with not one but two special one-year-only models. As it did with the last shark in '82, a Collector's Edition was offered, with special paint, wheels, upholstery, and badging.
The second special was called the Grand Sport, an homage to the racing Corvettes spearheaded by Duntov in 1962. The Grand Sports were finished in Admiral Blue metallic paint with a white stripe down the car's center and two red hash marks -- or "Sebring stripes" -- on the driver-side front fender. Grand Sport coupes were shod with black painted ZR-1 wheels and fitted with rear fender flares to cover the wider rear tires, while convertible Grand Sports received the standard Corvette wheel-and-tire package.
The Grand Sport was no mere appearance package, though. Under the hood was a highly modified LT1 with freer-flowing heads, bigger valves, a more aggressive cam, 1.6-ratio roller rockers, and high-flow intake manifold. Called the LT4, this Gen II swan song put out 330 hp and 385 lb-ft of torque, and it was dressed for success with bright red accents and a "Grand Sport" plate on the throttle body. While the pumped-up engine was initially planned as a Grand Sport exclusive, Chevy ultimately decided to install the LT4 in all six-speed Vettes for '96, while cars fitted with the 4L60E automatic received the standard LT1.
In addition to the C4, another Corvette legend passed in 1996. Zora Arkus-Duntov, whose legacy would forever be intertwined with his beloved sports car, died in April 1996. Duntov never did see his mid-engine dream car become a reality, but he was able to attend the opening of the National Corvette Museum in Bowling Green in 1994, which must have been deeply satisfying for the man who almost literally saved the Corvette from certain death in the mid '50s.