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Illustrated Corvette Series No. 165
"The Curious Case of the Greenwood G Cars"
John Greenwood is a Corvette racing legend. Actually, it was the “John and Bert” Greenwood story here because John’s brother Bert was very much part of the story. Through the ‘70s, Greenwood Corvettes were fearsome and very entertaining. It was a classic, American little guy vs the big dogs. The Woodward Avenue street racer put the fear of big-block Chevy power into the competition. While all of the above is correct, sometimes early childhood impressions have profound effects on a lad’s life.
The Greenwood brothers had an inside connection - their Dad. Sr. Greenwood worked at the GM Tech Center and on weekends would take John and Bert to see some of the prototype cars in development. (Can you imagine that?) The inspired boys started their careers with a tube frame go-cart, powered by a Briggs & Stratton lawn mower engine. Not long after getting his drivers license, John was street racing a big-block ‘64 Corvette. Street racing lead to road racing with John winning the A/Production championship in his first year.
With a sponsorship from BF Goodrich, Bert and John took their 427 ZL-1-powered Corvette. to Le Mans where the thundering Stars and Stripes 427 Corvette was an international sensation. The ‘70s was a Greenwood/Corvette decade with championship victories, wild, over the top cars, speed records, a burgeoning racing parts, turn key race cars, and street body kits business.
In the ‘80s, the sports cars world entered the era of the supercar., with cars such as the Ferrari F40, Porsche 959, Countach, and ZR-1 Corvette. All the while, John and Bert were secretly planning their own Corvette supercar. Their goal was to offer a Corvette that could be driven to Daytona, turn 200-mph laps, and driven home! Here’s where the story becomes somewhat hard to follow.
From ‘91 to ‘94 the Greenwoods teased the press with the G350sc, the G383, the G572, and a hyper-exotic version of the G572. There were two essential elements all four cars; first a super-rigid frame, and second, race car-like four wheel, coil-over shocks suspension with anti-dive and anti-squat 5-link suspensions. The G350sc was powered by a Vortech supercharged 350 LT1. The G383 used a Lingenfelter LT1 stroked to 383-CID. But the big dog was the 575-HP, all-aluminum Keith Black 572-CID big block. The second version of the G572 never made it past the prototype stage but was to be powered by a 700-HP all-aluminum big-block Chevy, with an exotic cross-ram fuel-injection system. All of the cars were equipped with race-ready Turbo-Hydramatic automatic transmissions. Each car was just dripping with racing hardware, the biggest available tires, wheels, and brakes, and could be the subject of long detailed articles. Everything the Greenwood brothers knew about how to make brutally fast racing Corvettes was applied to their version of what an all-American supercar should be.
There was no mistaking that these were no ordinary Corvettes. Bert Greenwood was the team’s aerodynamics specialist and messaged and tweaked the airflow around the cars with attention to every surface. All corners and edges were rounded and faired in. The front air dam with its integrated driving lights kept airflow under the car to a minimum while the rear belly pan vented air out the back. Forward mounted hood scoops fed the engine’s air intake and hood vents relieved under the hood air pressure and helped cool the engine. The rear wing was elaborately mounted to the aft portion of the frame, not just the body. Bert even made carbon fiber fairings for the windshield surround, the side windows, and the rear glass.
For all of the racing hardware, the car’s interiors were quite lush, trimmed in bright colored leather, suede, and wood grain panels. Extra sound deadening material was added to keep the interior as quiet as possible. These were to be grand touring (GT) cars, not race cars.
So, what happened to all of the Greenwood G cars? First of all, they were very expensive. A ‘90 to ‘95 Corvette has a base price between $32,000 to $37,000. The G350sc was priced just over $100,000 and the G383 had a starting price of $130,000. But the super exotic G572, the prototype version, had a proposed price of $425,000! A few orders were placed for the G350sc and G383. The G572 had no takers and the where abouts of the prototypes are only known to the Greenwoods. It turned out that John couldn’t quite turn off his drive to innovate and was always working on the next great enterprise and not completing his previous innovation. In retrospect, what the dynamic duo really needed a business manager. Since the introduction of the C5 and C6 Corvettes, the Greeenwoods have produced a line of body kits with parts that look very much like the elements found on the C4 G cars. In the end, less than a handful of C4 G cars were actually produced. - KST
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lllustrated Corvette Series No. 91 - 1990 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 Bridgestone test track in Texas 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! - KST
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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 the Big Doggie Corvette 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 Corvette'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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Illustrated Corvette Series No. 81 1990 Corvette
"In the Shadow of the ZR1"
The introduction of the C4 '84 Corvette in the autumn of 1983 saved the car's reputation as a true sports car. Every succeeding year, things got just a little bit better, and the '90 Corvette was no exception. Unfortunately, it stood in the shadow of the ZR-1.
Chevrolet had been stoking the Corvette fans since 1988 with the news of the soon-to-arrive "Super Vette," the ZR-1. What seemed like embarrassing delays only served to create a mountain of expectation for the car. Consequently, the "regular" Corvette got as much attention as Frank Sinatra, Jr.
The ZR-1 aside, Chevrolet had a great selection for Corvette buyers for 1990. To start off with, the car did not have another big price jump. The new list price for the '90 Corvette was $31,979 up only $434 from 1989. The Z51 handling package was reduced by $115 to $434. On the other end of the options scale, the ZR-1 cost an EXTRA $27,016! The Callaway Twin-Turbo option cost $26,895!
Even though the ante for a super Corvette was as much as an 84-percent premium over the stock version, Chevrolet public relations spin masters were quick to point out that a nearly $60,000 Corvette was a bargain compared to a Porsche or a Ferrari.
Like previous C4 Corvettes, the '90 model was peppered with small improvements that all added up to a better sports car. Under the hood, the fuel-injected L98 engine got another five horsepower as a result of adjustments in the air- intake speed-density control system, increased compression, a modified camshaft, and less restrictive exhausts. The new sloped-back radiator design eliminated the need for a heavy-duty radiator. Also, the radiator boost-fan was now standard. The 17-inch wheels were lighter than the previous year and the selective ride, andhandling package provided ride quality for everyone.
The interior received a new wraparound dash with analog gauges in front of the driver and digital gauges in the center console. The new steering wheel had the first generation airbag and the car now had a real glovebox. It was also the first year for the new Bosch-Delco 200-watt CD player and the oil gauge now measured useful oil life.
The '90 Corvette with a six-speed transmission and the optional handling package would have been the Corvette flagship were it not for the ZR-1. This was a solid 150mph sports car with the bargain price in the low-$30,000 range. - K. Scott Teeters
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lllustrated Corvette Series No. 82 1990 ZR1 Corvette
Whether is was deliberate or accidental, Chevrolet milked the automotive press for nearly two years with the ZR-1 Corvette! It was the biggest power leap since the introduction of the big-block engine in 1965.
The ZR-1 conversion was much more involved than simply dropping a larger engine under the hood. The biggest challenge had to do with actual production. The original idea was to have a set of double-overhead-cam heads made that would replace the stock Corvette heads. But they soon discovered that the extra width from the new heads made it impossible to install the engine on the assembly line. Changing the assembly line or the frame was not an option. So the decision was made to have a completely new engine developed.
Since GM owned Lotus, work began in May 1995 by Lotus engineers to design a new engine for a super-Corvette. The new engine would be designed to fit into the Corvette assembly line, but the overall package would be far from cheap. Unlike the Cosworth Vega's DOHC bolt-on heads, the new LT5 would be a fresh start.
Even though the introduction was delayed because Chevrolet wanted to get it right, the finished product was stunning. The L98 Corvette engine had 245 horsepower, the ZR-1 packed 375 horsepower! The engine had four overhead-cam shafts and 32 valves. The heads used a fast-burn cloverleaf design with centrally located spark plugs. The intake manifold had 16-runner inlets and two Multec injectors per cylinder. It had a direct-fire ignition with camshaft sensors and used 12 quarts of oil. The ZR-1 was a jewel of an engine.
To handle the extra power, special 315/35 ZR17 Goodyear Z-rated tires were mounted to 11-inch wide rims. To cover the larger tires, new body panels were made to replace the stock doors, rear fenders, rear fascia, and upper rear panel. The taillights were rectangular, as were the exhaust tips. All of the Z51 suspension parts were standard.
The ZR-1 was a real bear. It ran the quarter-mile in 13.4-seconds and 0-to-60 in 4.9-seconds and. Top speed was 171mph. Despite the $58,8741 price, it didn't stop 3,049 customers from buying a 1990 ZR-1. - K. Scott Teeters
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lllustrated Corvette Series No. 83 1990 ZR1 Engine
"The Power of the ZR1"
Not since the glory days of the 1967 to 1969 427/435 engine, had there been such an impressive sight as the LT5 engine. Corvette designers knew that they would need a very special engine to put the car into world-class territory. To expedite the process, Chevrolet established the parameters and had Lotus complete the details of the new engine design. Assembly of the racer-like engine was subcontracted to boat engine maker, Mercury Marine of Stillwater, Oklahoma.
The Mercury Marine 21,000 square foot facility used state-of-the-art machine tools with extraordinary tolerance capabilities. After the block and heads were machined, they were examined with a Cordax measuring machine that checked every three-dimentional measurement in only 45 minutes. Next was a six-step assembly process.
First, the heavily ribbed short-block was assembled with aluminum cylinder sleeves coated with Nikasil, a nickle-silicon alloy. The crankshaft and connecting rods were forged steel, and the pistons were aluminum. The five main bearings were held in place with an aluminum cradle that attached with 28 bolts. Next, the double-overhead-valve aluminum heads were assembled. Each bank had two camshafts, one for the intake valves, and the other for the exhaust valves. The valve stems were actuated directly off the cam lobes.
During the third step, the assembled heads, valve train, and cam covers were installed. The fourth and final assembly step saw the installation of the ignition hardware, alternator, the complete induction system, and other accessories. The electrical system was then computer checked, followed by a dyno test. The completed engine had a 14-minute dyno test for initial startup, break in schedules, and a full-throttle run to establish power rating.
The new LT5 engine measured 350 cubic-inches, and was rated at 375 net horsepower. Aside from the details, there are several other very unique aspect of this engine. Not only was it a nearly completely hand-made engine, but the LT5 was the only official Corvette engine that was not built by Chevrolet. Measured the old way, the "gross" power was close to 500!
In March of 1990, with a nearly stock ZR-1, Tommy Morrison showed off the LT5's capability by setting several speed records. His 5,000-mile average speed was 173,791 mph. His 12-hour record speed was 175.573 mph, and his 24-hour record speed was 175.885 mph. These record had previously been held by for over 50 years by Abner Jenkins and his V-12, 1,570 horsepower aircraft engine powered racer. The new production ZR-1 had plenty of grunt to set speed records and run with anything on the road. - K. Scott Teeters
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lllustrated Corvette Series No. 84 1990 CERV III
"Over the Top Design"
The CERV III was a real-world version of the Corvette Indy show car. The Corporate Engineering Research Vehicle III (CERV III) was more than pretty show car; it would be the most advanced Corvette study to date.
Chief of Chevy III Studio, Jerry Palmer, handled the styling details while Dick Balsey was the engineer on the project. The objective was to showcase the Chevrolet design team and Lotus' advanced racing experience. This was no easy task, by any means.
The nose of the Indy had to be shortened and the side windows flattened out so that they could go down into the doors. The wheel openings had to be opened up to allow 3.5 inches of travel and the rocker panels reshaped to accommodate side-mounted fuel cells. Also, the overall height had to be increased a few inches.
The CERV III's hardware was just as exciting as the body shape. To start, the LT5 engine was treated to two Garrett T3 turbochargers that bumped the horsepower up to 650 and the torque to 655 lb-ft. The 3,400-pound CERV III ran 0 to 60 in 3.9 seconds, had a top speed of 225 mph, and had 1.1 gs of lateral acceleration!
Since the car was completely built by Lotus in England, carbon fiber was used everywhere possible, just like a race car. The underbody was carbon fiber with a fiberglass-finish coating. The classic Lotus backbone chassis was made of carbon fiber and weighed only 38 pounds.
Although the suspension looked normal, the springs and A-arms were made of titanium. Actuators were used in place of shock absorbers and were connected to a state-of-the-art computer-controlled active suspension system. ABS braking and traction control was also part of the package. The transverse-mounted engine used a six-speed automatic transmission for all-wheel-drive and four-wheel steering.
The completed car was more than anyone expected, especially the bean counters. Cost estimates put the price tag between $300,000 and $400,000, making the world-class CERV III the most expensive proposed Corvette ever! - K. Scott Teeters
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lllustrated Corvette Series No. 85 - 1990 Callaway Twin-Turbo
While the ZR-1 was getting all of the attention from the automotive press, Reeves Callaway was quietly building his own "blessed by Chevrolet" super-Corvette, the Callaway Twin-Turbo.
The ZR-1 was distinctively European inspired. The all-aluminum, double-overhead-cam engine reflected a different approach to speed. The Callaway effort was uniquely American. It started off with a great pushrod performance engine and add lots of go-fast parts. Both ways get you to 180mph. One version is subtle, the other is not. Both were available from your local Chevy dealer!
Styling was another distinction. As amazing as the ZR-1 was, to the untrained eye, it was just another Corvette. The Callaway aero body kit had all sorts of vents and scoops that let the everyone know that "something special" is inside." The price of admission was similar as well. Priced at $26,895, the Callaway option cost $121 less than the ZR-1. But a loaded Callaway went for over $66,000!
Callaway blueprinted and balanced the stock Corvette engine then added a new forged steel crankshaft with new 4-bolt main bearing caps, and Mahle 7.5:1 compression pistons. Aluminum heads with new valves and springs finish off the main block. Then the real meat is added. Twin Rotomaster turbos and intercoolers finished off the top of the new engine. A Callaway Micro Fueler II fuel pump worked through stock injectors. The Z51 chassis option added a power steering cooler, stiffer spring rates, larger front brake rotors and calipers. A GM/ZF 6-speed transmission was used, along with the factory adjustable suspension. The custom body kit finished the exterior while the interior was stock.
Only 58 units were sold in 1990, making this a very rare, very expensive, 180mph Corvette! - K. Scott Teeters
lllustrated Corvette Series No. 86 1990 Sting Ray III Concept Car
Designing the "next Corvette" is a never-ending job for the elite Corvette Design Department. It's also one of the most challenging design tasks in Detroit. Between the egos and budget concerns, it's amazing it ever gets completed.
The late '80s and early '90s were some of the worst economic times GM had ever experienced. The management chess game was mind-boggeling. Dave McLellan was unsuccessful in fulfilling Duntov's vision of a mid-engine Corvette and retired in '92. GM's new president, Bob Stemple put the C5 project on hold while the GM cash-crunch was solved. No one was sure of when the next Corvette would hit the road, despite many attempts to define the new design.
The task-master for the new Corvette was Chuck Jordan, know as the "Chrome Cobra." Jordan secretly staged a 3-way C5 internal competition between John Schinella's Advanced Concepts Center, Tom Peters' Advanced 4 Studio, and John Cafaro's Chevy 3 group. The designs were unique and the competition was fierce. Schinella's California-based studio concept, the "Sting Ray III" was the first design completed and was well received at the '92 Detroit International Auto Show. However, the Detroit-based design groups were less than thrilled with the car.
After the structure and drive-train placements were determined, a series of styling sketches were made, presented, debated, and finalized. Next a full-size clay model was built to work out the styling details. The completed shape had to look "new," yet had to have traditional Corvette styling elements. The curves and fender budges were reminiscent of the Mako Shark II cars of the mid-'60s. Once the shape was completed, a running prototype was built.
The backbone chassis and the engine-transaxle placement determined the proportions of the car. With the heavy side rails gone, interior access was much improved. The wheelbase was a 6.8-inches longer, the length increased by 2-inches, the width grew by .9-inches, and the height was .8-inches taller than a stock Corvette. Most notable was the long, slopped windshield, the narrow fixed headlights and the roadster-only roof design. Unfortunately, there was a V6 under the hood.
The Sting Ray III never came close to production, although the new C6 now has fixed headlights. But a good design is never wasted. The basic shape became the Cavalier convertible. I'm sure that's not what Schinella had in mind. - K. Scott Teeters
lllustrated Corvette Series No. 87 1990 Mears-Shinoda Corvette
"Larry Shinoda Strikes Again"
The Rick Mears Special Edition came out of an interesting mix of talents. Mears, a three-time Indy 500 winner, was the front man, Corvette designer Larry Shinoda was the stylist, and Jim Williams was the businessman. While this certainly wasn't the first body kit for a Corvette, it was one of the cleanest. Mears was at the top of his racing game by the early '90s. Rick won the Indy 500 in '79, '84, '88, and '91! He was the Indy 500 "Rookie of the Year" in '79, and racked up six Indy 500 pole positions. Mears retired from racing in 1992 with 29 CART wins and 40 pole positions.
Larry Shinoda is generally known as the designer of the 1963 Stingray. While this is correct, the actual Stingray shape was first drawn in 1957 by Pete Brock and Bob Veryzer as a concept study called the "Q-Corvette." Shinoda took the sketch and made it into a real car. Larry would go on the design the Corvair Monza show car, the Mako Shark, and the Boss 302 Mustang.
Jim Williams was the president and CEO of Golden State Foods, a food preparation company that services all of the McDonalds restaurants. In the late '80s, GSF was an associate sponsor of the Penske racing team.
Shinoda showed some sketches to Williams and Mears at the Long Beach CART race in 1989. Both men liked the design and agreed to go into business. Shinoda-Williams Design, Inc. was formed and started making kits in 1991.
Shinoda's design wasn't just another make-over kit. The front and rear spoilers, along with the sculpted side panels lowered drag coefficient from .34 to .30! As a throwback to his old Mako Shark days, Larry gave the side panels some "coke bottle" style. All of the parts were barrier crash tested and designed so the the stock Corvette tire jack could be used. Except for the front chin spoiler, the factory ramp angles were maintained.
The kit was made up of 11 pieces that would attach to any '84 to '91 coupe or roadster. The panels were made from primed, semi-rigid polyurethane material. Also included were front fog lights, black finished stainless steel exhaust tips, floor mats with the Mears logo, a "Shinoda Design" badge, a "Rick Mears Special Edition" badge, and fasteners. Assembly time was 25 hours. The kits were designed to use common garage tools, used stock mounting points, and required little drilling.
The cost of the kit was $5,200, plus $2,500 to $3,000 for installation. Paint was another extra. The total cost for entire kit project was around $10,000. That's why not many kits were sold. In the early '90s, all regular Corvettes were under the shadow of the ZR-1. Extra money usually went under the hood. Shinoda pitched the kit to Chevrolet as a 1992 RPO option. They passed. - K. Scott Teeters