The 1985 Corvette

The Overview

The 1985 Corvette is the 1984 with the complaints answered. The biggest answer was under the clamshell: the Cross-Fire Injection 350 was replaced by the L98, the same cast-iron small-block with Tuned-Port Injection, a GM system built around Bosch parts – a hot-wire mass-airflow sensor, eight Bosch port injectors fed from a cast-aluminum plenum through long, curved tuned runners that packed the cylinders at low and middle speeds. It made 230 hp at 4,000 rpm and 330 lb-ft at 3,200, up 25 hp and 40 lb-ft, and it did it on less fuel; “Tuned Port Injection” badges replaced “Cross-Fire Injection” on the fenders, the only external change. The 700-R4 overdrive automatic stayed standard, and the Doug Nash 4+3, now with a reprogrammed overdrive controller, the switch moved from the console to the shift knob and a stronger 8.5-inch Dana 44 differential, was again a no-cost option, taken by 9,576 buyers, about one in four.

The chassis was tuned to the road rather than the test track. Base spring rates fell 26 percent at the front and 25 percent at the rear, with shock valving to match, and even the Z51 Performance Handling Package was softened, its larger front and rear stabilizer bars restoring the roll stiffness the softer springs gave up; Z51 now put 9.5-inch wheels at all four corners with Delco-Bilstein gas shocks and heavy-duty cooling, and because the 16-inch wheels and Goodyear Eagle VR50 tires were now built into the base price, its cost fell from $600.20 to $470.00. John Heinricy’s engineers dropped the car three-quarters of an inch, cutting the drag coefficient to 0.33, added a degree of caster for straight-line stability, fitted a bigger brake master cylinder and booster, and went after the squeaks and rattles. Inside, the digital instrument graphics were redrawn for legibility and the Lear Siegler sport seats could at last be had in leather.

The press noticed. Car and Driver ran the quarter in 14.1 seconds at 97 mph in an automatic, saw 150 mph, and called the Corvette the fastest production car in America, a claim that reportedly sent Porsche engineers to buy two 1985s and ship them to Weissach for a teardown. The price rose to $24,403 (about $2,000 more than the real 1984 figure once the mandatory wheel package is counted), the seventeen-month first year was over, and production settled to 39,729, still more than any year from 1980 to 1982. Three in four buyers took leather; nine in ten took the Bose stereo. Today the 1985 is the first C4 most people should buy: all the 1984’s hardware with the engine it should have had, the ride it should have had and the same low prices, a few thousand dollars above a 1984 and well below the 1986–87 cars with their convertibles and anti-lock brakes.

The 1985 Corvette Story

While there were few who questioned the technological superiority of the 1984 C4 over earlier generations of Corvette, its lack of robust horsepower and outright performance left many questioning this new version of America’s most beloved sports car. Chevrolet listened to the criticisms and quickly began to revamp the Corvette platform to become a more competitive contender.

After all, the U.S. economy was beginning to rebound from the recession that had plagued the United States (and indeed, the entire world) in the early eighties. The cost of fuel dropped as the world economy saw an oil glut – the result of conservation after the 1970s energy crises. This new oil surplus (and corresponding drop in fuel prices) quickly brought back buyers who were once more looking for big, powerful, performance cars.

In addition, Ronald Reagan and his administration had convinced Japanese automakers to voluntarily limit their car exports to the United States via the Voluntary Restraint Agreement (VRA), which had the intended result of encouraging American consumers to purchase American-made automobiles.

When the C4 Corvette returned for a second year in 1985, it did so with some much needed improvements.

Gone forever was the Cross-Fire Injection System that had been introduced as part of the C4 only a year earlier (and survived a single production year on the C4). Replacing this awkward and somewhat uninspired system was a new “Tuned Port Injection” system built around Bosch components, with a new intake manifold. This new system provided an individual fuel injector for each engine cylinder, featured tuned runners and included a new mass air flow sensor, all of which would aid in the car’s improved performance.

In fact, the introduction of the new “Tuned-Port Injection” system improved the engine output by 25 horsepower, pushing the engine to a total of 230 bhp at 4,000 rpm. Similarly, the engine’s torque was increased by 40 lb-ft, to 330 lb-ft at 3,200 rpm (versus 290 lb-ft at 2,800 rpm on the 1984). The fact that these changes were so extensive, and that they had dramatically improved Corvette’s performance, motivated Chevrolet to use an entirely new designation for the engine – and thus the L98 was born.

Just as the engine had received an overhaul, the Doug Nash 4+3 Overdrive manual transmission underwent a less radical, but equally important, upgrade to help improve its performance. For the 1985 model, the 4+3 received a heavy-duty 8.5-inch differential ring gear (the Dana 44, in place of the 7.875-inch Dana 36) for extra longevity. As a convenience factor, the transmission’s override button was relocated from the console to atop the shift knob. Further, the transmission’s onboard computer was reprogrammed to make the overdrive function less intrusive. Additionally, the electronics governing the lockup torque converter clutch were also revised.

Another item that General Motors sought to resolve in the 1985 Corvette was the car’s harsh, and often unforgiving, ride. Responding to the many complaints they received, Chevrolet softened both the spring and shock rates on all Corvettes – even those with the Z51 suspension package.

With regard to the Z51 package, other suspension changes were introduced as well. This option now included larger fore and aft stabilizer bars which helped to offset total roll stiffness after GM introduced the softer suspension calibrations. Further, the package now put 9.5-inch-wide wheels at the front as well as the rear. Also included were Delco-Bilstein gas-pressurized shocks and a revised heavy duty cooling system. The Delco-Bilstein shocks were also offered as a separate option on the base level Corvette.

Just as General Motors had made improvements to the steering and suspension systems, GM engineers continued to take great interest in how the C4 Corvette handled. After all, the C4 Corvette had been spawned off the design criteria that what it lacked in horsepower would be compensated for in car structure, design and drivability. As production of the 1985 Corvette progressed, the Z51 suspension package option continued to undergo revisionary design work, a process that was led by GM engineer John Heinricy. His intent was to develop the Corvette to a point where it could be classified as a “showroom stock GT car.”

Interestingly, the changes that Heinricy made to the suspension resulted in the 1985 Corvette being lowered ¾ of an inch. This change, though nearly indistinguishable to the naked eye, reduced the drag coefficient to 0.33. With the 3.07:1 rear axle, the 1985 Corvette could reach 150 miles per hour. Of course, achieving 150 miles per hour still required the upgraded rear end, but overcoming this particular speed barrier had been accomplished and solidified the C4 Corvette as a more serious sports car in the eyes of performance enthusiasts.

Did you know? The exterior styling of the C4 Corvette was completely unchanged from 1984 to 1985 with the exception of the side badges on the front fenders of the car, which were changed from Cross-Fire Injection to Tuned-Port Injection. Because of the harsh ride experienced by owners of the 1984 Corvette, the spring rates were decreased in 1985 - a 26% reduction in the front springs, a 25% reduction in the rear.

As GM engineers set out to have Corvette achieve higher speeds, it was determined that the steering caster angle should be increased by one degree (to a total of four degrees) to produce better straight-line stability. Similarly, the braking system was bolstered to produce greater braking power by the addition of a larger brake master cylinder and brake booster as well as different brake pad linings. These minor, but significant changes were just a few of the many considerations that GM engineers were making when responding to the criticisms they had received on the 1984 Corvette.

While the appearance of the C4 Corvette was well received by critics and enthusiasts alike, there were still several small refinements that were made to its cosmetic appearance. The interior received a minor facelift which included revised instrument graphics and optional leather upholstery for the more expensive Lear Siegler sport seats. Though subtle, these changes further solidified the overall aesthetic quality of the car. Additionally, Chevy engineers began seeking out and eliminating the sources of the rattles and squeaks that had been such a constant annoyance to consumers who had purchased the 1984 model.

Despite its many improvements, the 1985 Corvette was still met with a mix of praise and criticism. Reviewers complimented its improved braking and road handling characteristics. At the same time, they criticized the revised short rack steering. In fact, automotive testers claimed that the steering was too quick for around-town use. Further, the ride was still deemed as being overly harsh despite the refinements that had been made to the suspension system. Ultimately though, the overall opinion of the 1985 Corvette was that General Motors had improved on their earlier efforts and had taken the C4 in the right direction.

In 1985, the Chevy Corvette sold for approximately half of the comparably equipped Porsche 928, yet was capable of handling/performing at the same level as the German sports car. In fact, when doing a performance comparison of the 1985 Corvette and the Porsche 928, the Corvette outran the Porsche and was named the Fastest Car In America after hitting top speeds of 150 miles per hour. The result, combined with the Corvette’s return to racing in 1985, was – so the story went – unsettling enough that Porsche’s engineers bought two 1985 Corvettes, shipped them to Germany and took them apart in an attempt to determine what made them so quick!

Car and Driver magazine was among the automotive media that celebrated the new model’s improved automotive refinements. After sampling two Corvettes, one with an automatic transmission and the base suspension and one with the upgraded Z51 suspension and a manual transmission, they recorded results that were considered more than respectable for their time. The automatic ran a quarter mile time of just 14.1 seconds at 97 miles per hour. The manual version ran the quarter mile in 14.4 seconds at 95 miles per hour. Car and Driver went on to proclaim the Corvette America’s fastest production car, with a 150-mph top speed. In less than two years’ time, General Motors had succeeded in improving the performance of the C4 to a point where it could rival the competition worldwide.

One of the great challenges that was about to be set forth by General Motors was the development of an entirely new engine. After all, the current L98 350 cubic inch small-block V8, (with its cast iron block and its rocker operated valve gear), was nearly thirty years old and, despite the refinements of the fuel injection system at the beginning of the model year, was not the performance powerhouse that had become synonymous with earlier generations of Corvette. Still, Federal edicts of the day made the idea of reworking the generations-old V8 into something more powerful an unlikely course of action. Despite that fact, it was in 1985 that GM made the decision to begin the fundamental reworking of the 350 small block – and would ultimately lead to the development of an all new V8 engine.

It was decided that the revised engine would have to be capable of returning the same fuel economy as the L98 engine but would have to achieve the performance levels of Ferrari, Aston Martin and Porsche. In the words of Chevrolet engineer Fred Schaafsma, this new engine (and the Corvette it would power) was to be “…the best performing production car in the world.” Ironically, that reworking would impact the future of Corvette for all time, giving birth to one of the greatest Corvettes ever – the ZR1.

Production Volumes

The cost of these improvements brought a sizable increase in the price of the 1985 Corvette. The cost of the C4 (base price) jumped from $21,800 in 1984 to $24,403 just a year later. With the seventeen-month 1984 model year over, sales fell to 39,729, almost 12,000 fewer than 1984 but still more than any year from 1980 to 1982. Despite the decline in sales, General Motors knew that they were moving in the right direction with this new design, and continued to lay out further design revisions which would help the Corvette gain greater success in the years to come.