Corvette C4 (1984-1996)
The fourth generation Chevrolet Corvette was introduced at the close of 1982 production
as a 1984 model and ended in 1996, meaning that there's no such thing as a "1983
Corvette" (though 44 prototype 1983s were built, number 23 is the only survivor
and is housed at the National Corvette Museum in Bowling Green). The C4 Corvette
is known for its sleek look. Instead of fiberglass, it was made from reaction injected
molding plastics, a sheet molding compound. The C4 coupe also is the first Corvette
to have a glass hatchback (except for the 1982 Collector's Edition) for better storage
access. It also had all new brakes with aluminum calipers. The Corvette C4 came
standard with an electronic dashboard with digital liquid crystal displays for speed
and RPM. The C4 was a complete redesign of the previous generation, and the emphasis
was on handling. The C4 Corvette was proclaimed the best handling car ever when
it was released. This handling came with the benefit of a solid, uncompromising
ride. The unit-body frame used in the C4 was prone to rattles and squeaks due to
minimal sound deadening. Also due to the external unit-body frame, the door sills
were high and entry and exit have been likened to a "fall in and climb out" experience.
The emergency brake was relocated to between the seats in 1988 for easier entry
and exit. From 1984 through 1988, the Corvette was available with a Doug Nash "4+3"
transmission - a 4-speed manual coupled to an automatic overdrive on the top three
gears. This unusual transmission was a synergy that allowed corvette to keep a stout
4 speed, but add an overdrive. As technology progressed, it was replaced by a modern
ZF 6-speed manual. However, the C4 performance was hampered by its L98 250 hp (186
kW) engine until 1992, when the second-generation LT1 was installed, markedly improving
the C4s performance. 1996 was a high point of small block Chevrolet development
and the 330 hp (246 kW) LT4 was installed in all manual transmission cars.
During 1986, General Motors acquired Group Lotus, the U.K. based engineering consulting
and performance car manufacturing firm. The Corvette division approached Lotus with
the idea of developing the world's fastest production car, to be based on the C4
generation Corvette. With input from GM, Lotus designed a new engine to fit in place
of the L98 V8 that was powering the standard C4. The result was what GM dubbed the
LT5, an aluminum-block V-8 with the same bore centers as the L98, but with four
overhead camshafts, 32 valves. Lotus also designed a unique air management system
for the engine to provide a wider power band by shutting off 8 of the 16 intake
runners and fuel injectors when the engine was at part-throttle, while still giving
the ZR-1 a stellar 375 hp when at wide open throttle.
In addition to the engine, Lotus helped GM design the ZR-1's upgraded braking and
steering systems, and helped them pick the settings for the standard "ZX3" active
suspension system that Chevrolet was fitting to the car, helping to ensure that
the vehicle was more than just a modern-day muscle car with a big engine and no
real capability on the track.
GM found that the engine required special assembly, and that neither the Corvette
plant in Bowling Green Kentucky nor any of their normal production facilties could
handle the workload. Mercury Marine corporation of Oklahoma was contracted to assemble
the engines and ship them to the Corvette factory in Bowling Green where the ZR-1s
were being assembled.
The vehicle went on sale in 1990 and was available only as a coupe. It was distinguishable
from other Corvette coupes by its wider tail section, 11" wide rear wheels and its
new convex rear fascia with four square shaped taillights and a CHMSL (center high
mounted stop lamp) attached to the top of the hatch glass instead of between the
The ZR-1 displayed stunning ability both in terms of acceleration and handling capabilties,
but carried with it an astonishingly high price. MSRP for the ZR-1 in 1990 was $58,995,
almost twice the cost of a non-ZR-1, and had ballooned to $66,278 by 1995; it has
been rumored that some dealers successfully marked units as high as $100,000. Even
at base MSRP, this meant that the ZR-1 was competing in the same price bracket as
cars like Porsche's 964, making it a hard sell for GM dealers.
In 1991, the ZR-1 and base model received updates to body work, interior, and wheels.
The rear convex fascia that set the 1990 ZR-1 apart from the base model found its
way to all models, making the high-priced ZR-1 even less distinguishable. Further
changes were made in 1992, including extra ZR-1 badges on the fenders and making
traction control a standard feature, and in 1993, when Lotus designed modifications
were made to the cylinder heads, exhaust system and valvetrain of the LT5, bringing
horsepower up to 405. In addition, a new exhaust gas recirculation system improved
emissions control. The model remained nearly unchanged into the 1995 model year,
after which the ZR-1 was discontinued as the result of waning interest and the fact
that Chevrolet had never been able to sell them easily. A total of 6,939 ZR-1s were
manufactured over the six year period.
Not until the debut of the C5 platform Z06 would Chevrolet have another production
Corvette capable of matching the ZR-1's performance, however.