Before getting into repair discussions, I would like to tell everyone about the history of the C4.

The fourth generation Corvette began production in March 1983 as a 1984 model and production of the C4 stopped with the 1996 model year.  The 1983 model year was skipped due to quality and production problems.  No 1983 Corvettes were ever sold.  Chevrolet produced 44 test models for 1983.  All forty-four 1983 model year test cars assembled were crushed except for one (number 23, painted Arctic White), which was retired and put on display at the National Corvette Museum in Bowling Green, Kentucky, and it is still owned by GM.  Before being destroyed, a few cars were part of a press introduction at Riverside Raceway in California, in December, 1982.  Some were used to sort out production details while others were assigned to engineering for evaluation and crash testing before being crushed.  The stories that many people tell of having a 1983 or knowing of other 1983 Corvettes still in existence are just “Corvette urban legends.”

This first-year model of the C4 carried over the L83 engine from the third generation of Corvette.  The L83 engine had a unique fuel delivery method, named "Crossfire", a dual-throttle-body injection system. The Cross-Fire Injection (RPO L83) used two throttle bodies on top of the intake manifold.  The computer to drive the system was based on a Cadillac DFI unit and worked with GM's Computer Command Control.  CCC had been refined in 1982 to the extent that it had the ability to make fuel and air adjustments more then 80 times per second, compared to the previous year's 10 adjustments per second.  These advancements provided just 10 hp for Corvette, but it was the beginning of the upswing of horsepower and it provided a quick means for getting fuel injection back into the Corvette until the Tuned Port Injection was ready for production.

The C4 was praised for its sleek styling and its groundbreaking aerodynamic design.  With the first major body change since 1968 and the first major chassis and suspension change since 1963, the new C4 coupe incorporated a rear glass hatch for much improved cargo access, all new brakes with aluminum calipers, all-aluminum frame and suspension for weight savings and rigidity, and the first one-piece targa top with no center reinforcement.  The Corvette C4 came standard with an electronic dashboard with digital liquid crystal display for the speedometer and tachometer.  The 1984 C4 was a complete and total redesign except for its engine, and the emphasis was on handling with the introduction of the front transverse composite leaf spring (still used today on new Corvettes).  This handling focus came with the penalty of a harsh, uncompromising ride.

The 1984 and 1985 were the only C4's to lack the third brake light (CHMSL, Center High Mounted Signal Light) which was required by federal law beginning in 1986.  From 1984 through 1988, the Corvette used an unusual "4+3" transmission — a 4-speed manual coupled to an automatic overdrive on the top three gears.  It was designed to help the Corvette meet U.S. fuel economy standards.  The transmission was problematic and was eventually replaced by a much more modern “ZF” 6-speed manual gearbox in 1989.  This new transmission was also the first to feature Computer Aided Gear Selection (CAGS), which used a solenoid to lock out second gear during certain driving conditions.  This allowed the Corvette to maintain EPA fuel economy ratings high enough to avoid the "gas guzzler" tax.  Beginning in 1985, the 230 horsepower L98 engine with tuned port fuel injection was installed in most Corvettes, replacing the throttle body fuel injected “Cross-Fire” power plant.

In 1986 Corvette saw its 2nd Indy Pace Car, this time a convertible.  The first drop top since 1975, the pace car was available in several colors but not in a coupe.  It was also touted as the first pace car not to be modified for Indy Pace duty.  All 1986 convertible Corvettes are considered to be Indy Pace Car additions, regardless of color.  The Indy Pace Car driver of 1986 was retired Air Force General and test pilot Charles “Chuck” Yeager.  Chevrolet liked the idea of the first man to pass the speed of sound piloting the Corvette pace car for the Indy 500 so much that TV and print ads were made of Yeager and the Corvette.  Subsequently, Chuck Yeager became a C4 owner and a spokesman for AC Delco parts.

In 1987, the factory B2K option became available from the factory.  The Callaway Twin Turbo Corvette was a Regular Production Option (RPO B2K), the only time in Chevrolet's history a specialist manufacturer was entrusted with a technically advanced high performance RPO.  The B2K option was eventually replaced by the ZR1 option, though they coexisted from 1990 to 1991.  The early B2K's produced 345 hp and 450 ft-lb of torque.  The later B2K's produced 450 hp and 613 ft-lb of torque.

In 1986, the Corvette team approached Lotus, then a GM subsidiary, with the idea of developing an ultra-high performance vehicle based on the C4 Corvette.  With input from GM, Lotus designed a new engine to replace the traditional pushrod L98 V-8 that powered the standard C4.  The result was the LT5, an aluminum-block V-8 with the same bore centers as the L98, but with four overhead camshafts and 32 valves.  Lotus 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  375 hp when at wide open throttle.  Lotus also aided in the development of the ZR-1's standard "FX3" active suspension system.

GM found that the engine required special assembly, and that neither the Corvette plant in Bowling Green, Kentucky, nor any of their normal production facilities could handle the workload.  So 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, 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 taillights.

The ZR-1 displayed stunning ability both in terms of acceleration and handling capabilities, 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 ZR-1 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 the Porsche 964, making it a hard sell for GM dealers.

A 1990 ZR-1 set a 24 hour speed endurance record at the Firestone test track in Fort Stockton, Texas, using a relatively stock LT5 engine with modification that included removal of catalytic converters.  The Tommy Morrison racing team averaged 175 mph, including time for re-fueling and several driver changes.  In addition to the 24 hour record, additional international records were set in the C4 ZR-1:  100 miles @175.600 mph;  500 miles @175.503 mph;  1,000 miles @ 174.428 mph;  5,000 miles @ 173.791 mph (world record);  12-hour Endurance @ 175.885 mph.  These records remain unbeaten today by any production car, including the Corvette C5 and C6 Z-06 models.

In 1991, all Corvettes received updates to body work, interior, and wheels.  The convex rear fascia that set the 1990 ZR-1 apart from the base model was now included on L98 Corvettes, making the styling of the expensive ZR-1 even closer to that of the base cars.  This action by the makers of the Corvette angered many owners of the ZR-1.  The most obvious difference remaining between the base and ZR-1 models, besides the wider rear wheels, was the location of the CHMSL (center high mounted stop lamp), which was integrated into the new rear fascia used on the base model but remained at the top of the rear-hatch on the ZR-1s.

Further changes were made in 1992:  ZR-1 badges were displayed on both front fenders and traction control was added as a standard feature.  In 1993, Lotus redesigned the cylinder heads and valve train of the LT5, resulting in a horsepower increase from 375 to 405.  In addition, a new exhaust gas recirculation system improved emissions control.  Production of the ZR-1 ended in 1995, after 6,939 cars had been built.

1988 saw the 35th Anniversary Edition.  A limited number of cars was made, each with an ID number on a special badge next to the gear selector.  These Corvettes were easily identified as they were all white-on-white, with white wheels, and exterior trim.  Inside, seats, rugs, shifter and steering wheel were all white.

For the 1992 model year, the 300 horsepower LT-1 engine was introduced, which significantly improved the performance of the base C4 cars.  Also introduced in 1992 was Acceleration Slip Regulation (ASR), a form of traction control which utilized the Corvette's brakes, spark retard, and throttle close-down to prevent excessive rear wheel spin and possible loss of control.  The traction control device could be switched off if desired.  This feature caught many by surprise because the ASR would push the accelerator back up if traction to either rear wheel was lost.

After the production of the 1,000,000th Corvette late in 1992, there was more reason to party.  “We should all look this good at 40” was the ad slogan used to keep the party going for the 1993 Corvette. n1993 marked the 40th year of Corvette production, and the occasion was observed with the introduction of a 40th Anniversary Package (RPO Z25; $1,455.00).  General Motors designer Ms. Sara DeVries inspired the “Ruby Red” paint and trim package since the ruby gemstone is used to mark a 40th anniversary.  Why not make the anniversary model a ruby gem also?  Z25 cars featured a special "Ruby Red" paint, Ruby Red leather power sport seats with headrest embroidery, and special 40th emblems.  The leather interior on non-Z25 Corvettes also featured 40th anniversary embroidery on the seat headrests.  The emblems located behind the front wheels and above the beltline proudly displayed Corvette’s 40th year of production.  These were unique to the Z25 anniversary package, but liked so well by the public that may owners placed the emblem on non-anniversary models.  The Z25 option was available on both coupes (including the ZR-1) and convertibles; quantities were not limited.  Chevrolet produced 6,749 anniversary additions.