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Illustrated Corvette Series - No. 88 1991 Corvette - "'60s Performance, '90s Style"

Here's a shocker for you. While the ZR-1 was getting all of the attention, Dave McClellan and his team of engineers were quietly raising the performance bar. The stock 1991 Corvette could rip off a 0-to-60 time of just 5.3-seconds. That's quicker that a '69 427/435 big-block Corvette!

The country was in the doldrums in 1991. Recession, inflation, and federal deficits had a damper on the economy. SUVs hadn't arrived yet and very few people were interested in performance cars. Despite the bad mood of the economy, the Corvette was running better than ever. Corvettes usually only make incremental improvements and 1991 was no exception.

The most obvious change for '91 was the first facelift since the C4 Corvette arrived in '84. The front and rear bumper covers were restyled, there were new front fender vents, and new turbine-styled wheels. The formerly black horizontal body molding was now body colored and the rear bumper cover was styled after the ZR-1.

Other minor details included the placement of the third brake light at the top of the rear bumper cover. The list price for the '91 coupe was $32,455, up only $476 from the '90 model. The roadster started at $38,770. Total production was only 20,639, down 3,007 units from the '90 model.

Interesting were happening under the hood for '91. Although the power rating hadn't changed, new low-pressure mufflers improved performance and made the car slightly quieter. There was a new finned power steering cooler and a "low oil" sensor pickup was added to the oil pan.

The famous Z51 performance suspension option was replaced with the new Z07 option. The new option offered all of the Z51 suspension parts, plus the old FX3 adjustable suspension option. However, the suspension settings were "firm-to-very firm," and it wasn't cheap. The Z07 cost $2,155. Only 773 cars were ordered with this option.

1991 was also the last year for the official Callaway conversion Corvettes. Callaway also built the 500th Callaway Corvette on September 26, 1991. The ZR-1 market was cooling off as well. Only 2,044 of the $67,000 beasts were built in '91. That down from the 3,049 made in 1990.

The '91 Corvette had come a long way from the dog-days of 1981. Corvettes were winning races, there were two exotic Corvettes offered, and performance was better than ever. And just over the horizon, a famous old gun was about to return, the LT-1. - K. Scott Teeters

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lllustrated Corvette Series No. 89 - 1991 Callaway Speedster
"Going Out With A Bang!"

Reeves Callaway carved out an impressive spot in Corvette history. His Callaway Twin-Turbo (RPO B2K) had a five year run from 1987 to 1991. Chevrolet wanted to move the Corvette in a different direction, so Callaway decided to go out with a bang.

The Callaway Corvettes were as fast as nearly anything on the planet at twice the cost of a regular Corvette. Having the Callaway option on the Corvette order sheet was great, but with so much attention given to the ZR-1 and the new C5 being worked out, Chevrolet decided to end the run of turbo Corvettes.

Reeves unleashed a "hail Mary" pass at the '91 Los Angeles Car Show with his final Twin-Turbo Corvette, the Callaway Speedster. The car was designed for Southern California where it almost never rains, so there was no hard top available. Between the speedster top, the body panels, racing wheels, and over-the-top paint, the car was in "super car" territory.

Since this was to be his last BK2 Corvette, more juice was needed. Compression was bumped from 7.5:1 to 8.2:1. Airflow was improved 190 percent with new hood scoops. But he biggest challenge was the additional set of injectors and computer management system. The net result was 450 horsepower and 600 lbs/ft torque. Plenty! To top it all off, the engine was emissions certified for California.

The Speedster's stunning looks almost made what was under the hood irrelevant. Reeves had designer Paul Deutschman use his existing Sledgehammer nose and side panels as a base for the new speedster design. The most complicated part was the structural integrity after cutting down the windshield. Chevrolet assisted calculating the resonate frequency of the windshield posts at half height. A thin steel band across the top edge of the glass ties the two a-pillars together. A .75--inch rubber lip along the top edge of the windshield kicks airflow up by 5-inches. The glass is from a Corvette convertible and was modified by Libby-Owens-Ford, the supplier for the solar reflective windshield on the ZR-1.

Callaway explored several very loud paint colors, but was happy to coordinate the $7,500 paint option with the $12,000 German-made Connolly leather interior and wool carpeting.

During the 5-year Callaway run, there were 445 B2K option cars built, but Callaway made 510 Twin-Turbo Corvettes. The cost of the total Speedster package was $113,500! With 0-to-60 times of 4.4-seconds and a top speed of 185 mph, just don't stick your head up. - K. Scott Teeters

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lllustrated Corvette Series No. 90 - 1991 ZR2 Engineering Study
"Chevrolet's Big Doggie!"

Some Corvette engineers have all the fun. In the mid-'80s, Scott Leon was a Corvette Project Coordinator at the GM Proving ground in Arizona. Although the new C4 Corvette was a success, there were those that missed the old big-block Corvette power. But Scott Leon had a plan.

One night after work, Leon and his crew decided to see if a big-block engine would fit into the frame rails of a C4 Corvette. Using an old '84 mule Corvette, the crew was surprised to find that with only a few chassis modifications, the big rat motor fit into the Corvette. The engine was a real squeeze, but it worked. Leon wanted the car to be modern, so they cobbled together a tuned-port fuel injection unit with a modified aftermarket tunnel-ram intake manifold. With a little welding and a set of Buick Grand National injectors, the system worked.

The crude engineering study was enough for Leon to get management to agree to building a 454 prototype using a '86 Corvette Coupe with an automatic transmission. Later, another prototype was made using a '89 Roadster with a 6-speed transmission and a Z51 suspension. Now things were starting to get real interesting.

The final version of Big Doggie was a very impressive machine. Leon chose one of Chevy's marine 454 short-block and added a set of L88 aluminum heads. The engine assembly was modified so that all production accessories would bolt on. The only modifications to the car was to the floor pan and the right side of the frame rail, forward of the fire wall. Aside from the large raised hood, the package looked like a production car.Even under the hood, everything looks like it came off the assembly line.

The ZR-2's 454 engine was never dyno tested, but was estimated at 385 horsepower about the same as a ZR-1, but with a big difference. Big Doggie had much more low-end torque than a ZR-1 and pulled like a freight train. With the Z51 suspension parts and a 6-speed transmission, the car was a hoot to drive. To save weight, Leon used the optional hard top and removed the convertible mechanism.

Big Doggie's chances of it ever seeing its way into production was close to zero. Chevrolet had too many of its eggs in the ZR-1 basket and the big-block engine didn't meet federal fuel standards. For a time, there was talk of offering a retro kit. But ZR-1 performance at a fraction of the cost wasn't what GM was interested in. - K. Scott Teeters

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lllustrated Corvette Series No. 91 - 1991 ZR1 Speed Record Holder
"ZR1 Corvette Shatters a 50-Year Speed Record With a 175.885 mph Average 24-Hour Speed!"

Racing Corvettes have had a long history of durability problems. There are many accounts of Corvette racers setting track records and winning pole positions, only to have parts breakage put their cars out of the race. The success of the Showroom Stock and the Corvette Challenge cars proved that the new C4s had what it took to win long races. So it was only a matter of time before someone tested the new ZR-1 under racing conditions. Enter Morrison Motorsports.

On March 1 and 2, 1990, the Morrison Motorsports prepared ZR-1 Corvette shattered the 50-year old, 24-hour speed record with an astonishing average speed of 175.885mph with a "near-stock" ZR-1 Corvette! The details of the ZR-1 speed machine are a genuine testimonial to the quality of the new ZR-1.

In 1940, David, "Ab" Jenkins set the 24-hour speed record with his "Mormon Meteor III" racer. The huge 5,000-pound machine was designed by Augie Duesenberg and used a 850-horsepower, 27.5 litre aircraft engine! In 1940 Ab nailed the record with an average 24-hour speed of 161.18mph. The record stood for 50 years. Many attempted to break the record, and all failed... until the ZR-1 arrived.

The ZR-1 speed record attempt was the idea of Pete Mills, a west coast automotive writer. Mills saw potential in the new ZR-1 and pitched the idea to Corvette racer Stu Hayner. Corporate connections can be helpful. Hayner talked with Chevy's John Heinricy who pitched the idea to the right people inside GM. Tommy Morrison was also brought on board with the plan and the project was approved by the GM brass. The only change to the plan was to also run a stock L98 Coupe.

The FIA rules mandated that a speed record car must carry "non-consumable" spare parts in the event of a breakdown and the driver wasn't able to get back to the pits for repairs. Consequently, the ZR-1 had to carry an additional 300-pounds of spare parts in two suit cases lashed to the rear roll bar supports of the full roll cage! Drivers were expected to be able to fix the car if something broke.

The ZR-1 was essentially stock, with the exception of racing wheels and slicks, an EDS telemetry system, a 45-gallon fuel cell, and other assorted racing and safety parts. The suspension was stock, minus the anti-roll bars and the rear used a 3.07:1 gear set. Extra oil coolers and differential coolers were added and the headlights were replaced with racing lights. The stock L98 Coupe was similarly prepared.

The 7.71-mile Firestone test track in Arizona was chosen for the speed record assault. The track had 1.5-mile long straights and 2.35-mile curves that allowed the car to be driven nearly flat-out. There were three lanes to the track and no guard rails, making driving at high speed a concentration challenge. The L98 coupe ran for 6 hours before it was pulled so that it could be shipped to a car show in Geneva.

The ZR-1 ran nearly flawlessly for 24 hours with only one minor repair. At the end of the day, the 8-driver team broke 3 world records and set 4 FIA records. After breaking the records, Tommy Morrison took a 2-lap victory run at full-throttle! The ZR-1 Corvette was proven to be a solid performer. How sweet it was!