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Inspecting a Rare EX87 Development Corvette

Cruiser To Bruiser

Walt Thurn Mar 14, 2019
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The special Corvette featured here carries the General Motors VIN # EX87/5951. EX is the company’s identifier it attaches to vehicles used for experimental testing and these rarely leave the corporation. Employees working with these cars called them “Mules” and when the testing is completed they are destroyed. We will identify this test Corvette as EX87 so we do not confuse it with other GM test mules. Fortunately, our feature Corvette survived and resides in the Ken Lingenfelter Automotive Collection in Brighton, Michigan. His collection spans every Corvette generation and contains styling and test Corvettes. Each year Lingenfelter Performance Engineering conducts numerous charity events at this location. Attendees are invited to closely inspect this amazing assortment of unique automobiles. It is a successful fund raising destination for the Detroit metro area. For more information on their upcoming events visit www.lingenfelter.com.

EX87 played a major role in turning Corvette into a competitive sports car. It was used by Zora Duntov to test high-performance suspension, engine and aerodynamic parts. This testing was done under the direction of Chevrolet Chief Engineer Ed Cole. Like any test car this one led a tough test life. It was rarely seen in the public as it was being flogged around various Michigan and Arizona test tracks by Zora Duntov. However, its use as a test vehicle helped Corvette evolve from a six-cylinder cruiser into today’s sophisticated V-8 bruiser. The current C7 is a well mannered, comfortable and fuel efficient performance car. In addition it turns into a cross-country and track capable ride any time you push the start button. EX87 deserves a great deal of credit for Corvettes transformation.

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This prototype (EX122) named Corvette was unveiled on January 17, 1953. Large crowds attended GM’s Motorama Auto Show in New York City. (Photo courtesy of GM Archives)

To help place where EX87 fits into Corvette’s development history, let’s review how it was introduced to the public. It is a familiar story, but worth repeating. It started when a GM prototype named “Opel” (EX122) was secretly built in 1952. GM’s styling executive Harley Earl approved the Opel project. He wanted to infuse excitement into the stodgy Chevrolet brand. Earl named the finished prototype Chevrolet “Corvette” after a WWII British warship. It was introduced to the public on January 17, 1953. The unveiling took place at the GM Motorama Autoshow at the Waldorf Astoria Hotel in the New York City. If the public response to the Corvette was positive, Chevrolet was prepared to begin production in 1954. It was a public sensation and large crowds gathered around the stunning white convertible during the Motorama. One of these onlookers was a Belgian born Russian engineer named Zora Duntov. Zora was an accomplished engineer and a European sports car enthusiast. He applied for a job at GM several times to no avail. However after seeing the Corvette prototype he reached out to Maurice Olley, Director of Research and Development at GM seeking an engineering position. After several successful interviews Zora joined GM on May 1, 1953, as an assistant staff engineer for engine development with no Corvette responsibility. He reported directly to Maurice Olley and his starting salary was $14,000. Shortly after Zora was hired, three-time Indianapolis 500 winner and engineer Mauri Rose was hired by GM. His duties were to coordinate Chevy’s racing efforts. Rose was a racing legend in the U.S. and had many contacts within the racing community. One of these contacts was Smokey Yunick who owned The Best Damm Garage in Daytona Beach, Florida. This friendship between Rose and Yunick paid big dividends during Corvette’s future development.

All the pieces to this puzzle began coming together when Corvette production began in 1953. The new cars were assembled in the Customer Delivery Garage on Van Slyke Avenue in Flint, Michigan. The first car was completed on June 30, 1953. Three hundred were built in 1953 and were priced at $3,734, which included two mandatory options (heater and AM signal seeking radio). A total of 183 were sold by the end of 1953. Customers criticized the lack of rollup windows and the difficult to erect convertible top. Owners grumbled about the car’s lack of power. Undaunted by poor sales and owner complaints, Chevrolet moved Corvette production from Flint, Michigan, to St. Louis, Missouri, in 1954. Sales were forecast to be 10,000 units, but only 3,640 were delivered and many of those went unsold. Performance continued to be leisurely, with 0-60 times around 11.5 seconds, which was similar to a Chevy sedan. Focus on Corvette performance became a big concern when Ford introduced their two-seat V-8 powered Thunderbird in late 1954. Sales of Ford’s two-seat sports car quickly outpaced Corvette. The V-8 powered Thunderbird was quicker than the I-6 Corvette. This performance deficit changed when the 1955 Corvette was fitted with the 265ci/195hp small-block V-8 engine. It was 41 pounds lighter that the I-6 engine and produced 40 more horsepower and now performed better than the Thunderbird.

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Zora Duntov is at the wheel of EX87/5951 along with two engineering assistants at GM’s Arizona Proving grounds. Zora reached a top speed of 163 mph in this Corvette. Tape over the grille was used to improve airflow. (Photo courtesy of GM Archives)

Mr. Ed Cole was Chevrolet’s Chief Engineer and in 1955 he initiated an engineering campaign to transform the Corvette into a competitive sports car. One of the primary test vehicles he used to accomplish this goal was EX87. The Corvette was assigned to Chevrolet Engineering on October 28, 1954, from the unsold inventory of 1954 Corvettes. GM engineering gave it a prototype VIN number #5951 and it was added to the Chevrolet test fleet inventory. The aim was to use it to develop high-performance parts for the new small-block V-8 engine. Mauri Rose sent #5951 to Smokey Yunick’s shop in Daytona Beach near the end of 1954 to replace its I-6 engine with a 265ci small-block. Yunick also swapped the Powerglide automatic with a close-ratio three-speed manual transmission. This transmission became standard in all 1955 V-8–powered Corvettes. It was returned to Michigan and assigned to Duntov for testing. Zora used this prototype to evaluate engine, suspension and aerodynamic improvements for the Corvette. He was well aware of Corvette’s performance shortcomings, because of the exotic sports cars he worked on when he lived in Europe. He gave the Corvette a new identification number EX87/5951 for the project. His first order of business was to correct its poor high-speed handling by altering the front/rear suspension settings and their attachment points. During testing Zora discovered exhaust fumes were entering the cabin so he used yarn to identify the problem. He photographed the car in motion to watch how the yarn behaved. He found that moving the exhaust outlets to exit through the rear bumper stopped the cabin fumes. This exhaust outlet design became standard on all 1956 Corvettes.

Each year NASCAR sanctioned the Pikes Peak Hill Climb up the 14,000-foot mountain range in Colorado. Mr. Cole wanted to demonstrate Chevrolet’s high-performance capabilities and decided to attempt breaking the Pikes Peak record for unmodified sedans. He assigned Duntov to drive a camouflaged 1956 Chevrolet coupe equipped with the “power pack” 265 engine to attempt to break the record. Duntov drove the sedan up the mountain in 17 minutes and 24.04 seconds and beat the record by two minutes. It was a press bonanza for the dull Chevrolet brand. NASCR President Bill France was on hand and encouraged Chevrolet to begin participating in NASCAR events. Duntov wanted to run a Corvette at the 1956 Flying Mile event on the sands of Daytona Beach. He told Cole that he felt that the Corvette was capable of reaching 150 mph in the flying-mile event if it was properly prepared. Cole was skeptical but gave Zora permission to prepare and a test “mule” Corvette to test his theory. Corvette #5951 VIN was expanded to include EX87 for his project. It was delivered to assistant chief engineer Jim Premo to install a NASCAR kit on the Corvette. This included a tail fin/headrest, two cut down windscreens and a fiberglass passenger seat cover. Premo and his group added a precision tachometer on the steering column and a complete underside belly pan. They installed an early version of the 1956 225hp high-performance small-block V-8 and instruments to monitor engine performance. These included: underhood air temperature, fuel pressure, manifold pressure, water, oil and under-hood pressure gauges.

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In the early days of aerodynamic study, Zora replaced the windshield with a small windscreen and covered the passenger compartment. A large fin behind the driver improved stability.

Duntov performed high-speed tests with the revised Corvette at the Milford proving grounds. He discovered the engine was underpowered and unable to reach 150 mph. He designed the legendary Duntov camshaft to improve the engine’s top end performance. Ed Cole was encouraged by Duntov’s testing and decided to field a team of Corvettes at the 1956 Daytona Speed Weeks and 12 Hours of Sebring. Duntov determined he needed up to 295 hp to push the Corvette to 150 mph instead of the 240 hp in the current engine. He worked closely with John Camden who was an engineer in GM’s dyno testing center. Zora told John he needed 300 hp so Camden and his associates bored the engine to 307 cid. Duntov’s new camshaft was installed because it had a slightly lower lift, but much higher duration. This allowed the engine to rev to 6,500 rpm without valve float. The cylinder heads were ported and polished and the compression ratio was upped to 9.23:1. When Duntov visited John in the dyno room Camden reported the engine was producing 305 hp. Duntov was elated and on December 20, 1955, he recorded a top speed of 156.16 mph with a 2.92:1 rear axle. Later, he achieved a speed of 163 mph with a 3.27:1 rear axle. With the top speed goal reached EX87/5951 work was complete. All of its top-speed hardware was removed (except the fin) and transferred onto to a 1956 Corvette (6901) that was to compete at Daytona. The body of EX87/5951 was removed and installed onto a 1955 chassis VL55S001399.

What were the results of all this research and development that Zora completed on this 1954 Corvette? Duntov drove 6901 to a two-way average speed on the sands of Daytona Beach for a two-way average speed of 150.533 mph. This Corvette won the Mens Production Sport Car Class; Flying Mile and Duntov used EX87/5951’s vital components to capture this victory. When testing was completed, GM refurbished EX87/5951 and donated it to NASCAR for promotional duties. When NASCAR finished using the Corvette it was sold to Duane Church of Wilkesboro, North Carolina, where he drag raced it for several years. It went through two more owners before it was donated to the Bible Broadcasting Network (BBN) for promotional use.

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A small blister was added to the passenger cover to allow room for the raised part of the instrument panel.

After Yunick passed away in 2001 EX87’s original record setting engine was purchased from his estate. The 307-cid was marked “Record Run” on the bellhousing. The body was retrieved from the BBN and reunited with its original engine, restored and eventually purchased by Ken Lingenfelter. Since Ken purchased this historic Corvette it has won several significant awards. It won the Grand Sport Trophy at the Amelia Island Concours for its contribution to Corvette history. This Corvette was named as one of the 50 most significant Corvettes built since 1953 at the Great Hall ceremony the 2014 Bloomington Gold Corvette show. Ken told Vette, “I love loud cars and this car produces great noise. You really have to work at driving it as it has no power steering or brakes and the steering is vague. The engine is powerful and loud, but the best part is the father of our beloved Corvette developed and drove this car, it does not get much better than that.” Vette

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To gain access to the trunk the fin had to be removed. The rear exhaust outlets between the rear bumpers were filled in and replaced by 1956 bumpers with exhaust outlets that were under the taillights.

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The original GM Engineering VIN #5951 tag can be seen attached to the engine compartment firewall when the hood is opened.

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Because the passenger compartment was covered for aerodynamics, the door could only be opened by reaching under the cover in the cabin to pull the door latch.

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EX87 was not fitted with a rollbar. The only safety equipment was a seat belt. The fiberglass cover covered the dash and included a small windscreen.

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This view shows how the fiberglass cover secures the small windscreen to the cowl. It is held in place with screws.

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Once the door is closed the driver is out of the wind for better aerodynamics. The precision tachometer on the steering column was the main instrument Zora used during his speed tests.

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Standard seating was used in this prototype and did not provide much support for the driver. The headrest provided a place for Duntov’s head to be held when the wind pushed it back at 150+ mph.

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Remnants of the original 1954 interior were still inside EX87’s cabin. It was also a secure place for Zora’s cigarettes.

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The only way to open the passenger door with the passenger cover attached was to reach it from the driver’s side to pull the latch handle.

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After the body of EX87 was added to a 1955 Corvette frame, that cars #1399 VIN plate was added to the Corvette.

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The precision Stewart-Warner tachometer allowed Zora to carefully monitor the 307ci engines rpm. The new “Duntov Cam” allowed the engine to rev to 6,500 rpm.

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A close-ratio three-speed manual transmission became standard in all V-8–powered 1955 Corvettes. EX87 was fitted with one of these early units.

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Factory gauges were supplemented with Stewart-Warner gauges on the dash. However, their location probably made it difficult to read them when the car was at speed.

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You are looking at the office where Zora worked and helped transform the Corvette from Cruiser to Bruiser.

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This 307/305hp small-block was re-covered from legendary Smokey Yunick’s estate after he passed away in 2001. The engine was reunited with EX87 prior to its restoration.

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The small-block Mouse Corvette engine was 41 pounds lighter was the I-6 cylinder engine it replaced and produced more horsepower.

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This Carter four-barrel carburetor with a temperature sensitive choke (the round cylinder with a black cover at the top of the photo) feeds this 307ci engine.

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EX87’s electrical system was converted to 12-volts from 6-volts when it’s V-8 was installed. All V-8 Corvettes had 12-volt electrical systems. The tachometer drive is attached to the rear of the generator.

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A single line brake cylinder was used to activate the four-wheel drum brake system. Power brakes were not available for Corvette in 1955.

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This bumper assembly was added to EX87 to experiment with how the exhaust exits the Corvette. This design became standard on all 1956 Corvettes.

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Reinforced steel wheels were used for testing and high -peed Firestone tires were utilized during the testing.

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This aerodynamic fin helped keep the Corvette straight when it encountered crosswinds while it was testing at high-speeds. It had to be removed to open the trunk.

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This special license plate identifies the unique history of this Corvette. It includes its early GM engineering VIN # EX87/5951 and it 1955 chassis number ending in 399.

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The “tea strainer” factory headlight covers were replaced with these aerodynamic units on EX87 to smooth the front airflow on the Corvette.

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Ken Lingenfelter departs the Amelia Island award area after receiving the Grand Sport Trophy. Amelia deemed this to be “the most significant historical Corvette” of the event. (Photo courtesy of Walt Thurn)

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Ken Lingenfelter accepts his Great Hall gold medallion and certificate at the 2014 Great Hall award ceremony. Bloomington Gold President Guy Larsen is on the left and Great Hall founder David Burroughs is on the right when Ken accepts this honor. (Photo courtesy of Walt Thurn)

Photography by Robert McGaffin

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