1978 Greenwood Turbo GT - Rare Air

This One-Of-Three Greenwood Turbo GT Broke New Ground For Corvette Forced-Induction

Wayne Ellwood Dec 1, 2008 0 Comment(s)
Vemp_0812_01_z 1978_greenwood_turbo_GT Front_view 1/13

Rare cars make for good stories. And when the vehicle in question is a one-of-three unit no longer thought to exist, the tale becomes downright incredible. That's exactly what happened with Corvette collector Roger Abshire's latest find, the third and final Greenwood Turbo GT.

Abshire located the car in Long Island, New York, more or less by accident, late in 2004, while trolling the Internet for a Duntov steering wheel. When he typed the word "Duntov" into a search engine, this car came up. It was being offered for sale by a company in Long Island that dealt primarily in used limousines but took other cars in trade as well.

Vemp_0812_02_z 1978_greenwood_turbo_GT Engine 2/13

Blow-through turbo designs were complex for the era. Note the custom aluminum hat on the sealed carburetor.

It didn't take much examination for Abshire to realize that the car was not a Duntov. Yes, it had the requisite headlight buckets, but too many other features were incorrect for that model. As he carefully scanned each one of the 95 high-quality photos that had been posted with the ad, Abshire began to think the car might be a Greenwood Turbo GT. But when he talked to his various contacts, most of them told him that the third GT-the only one unaccounted for-had either been lost or destroyed. After all, no one had seen it in more than 20 years. But Abshire enjoys the research. For him, it's half the fun of collecting.

There were two obvious starting points. First, the numerous photos revealed a long list of specific features, almost all of which were Greenwood in design. Second, there was the auction company that was offering the car for sale.

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The trim tag shows a Mahogany cloth interior as being correct for the '78 Turbo GT. Greenwood ads referred to the color as "Saffron."

One of the photos was a clear shot of the trim tag. Even though the car was now painted black, the tag indicated that it was originally Burgundy, the color used on the third GT. In fact, Burgundy paint was (and still is) visible on the car where the black had worn off. The trim tag also showed a Saffron cloth interior, also correct for the GT. More photos showed coilover Koni shocks, a four-link suspension, and twin fuel pumps-all Greenwood essentials.

Abshire then called Mike Guyette, who owns the second GT, as well as John Greenwood. Greenwood was confident that the car was correct based on the photos of the rear suspension, but to be sure, he referred Abshire to Bart Lea, owner of longtime Greenwood collaborator ACI. Lea had firsthand knowledge of the car, since his company had built it. Guyette and Lea took the same approach. They asked questions about items they knew were unique to the third Turbo GT. When Abshire was able to locate every one of these pieces in the photos, they became convinced that this was the right car.

Vemp_0812_04_z 1978_greenwood_turbo_GT Rear_view 4/13

Lea then referred Abshire to Dennie Willard, the ACI engineer responsible for the car's fuel system, and former ACI marketing rep Michael LaEnvi. As Abshire told each of them about the car, they were able to confirm that it had various features specific to the third Turbo GT. In Willard's case, these included the motion-detector alarm, the fuel-management system, and the special decorative center caps for the wheels.

The fuel system, in particular, was a clincher. Willard had worked hard on the car's pressurized carburetor, which was an update of the unit used on the earlier models. Dual fuel pumps helped manage fuel delivery. The car normally ran on one pump, but when the turbo created enough pressure, the second pump was triggered by a system that keyed turbo boost to manifold vacuum. This pump fed a second set of fuel lines to the carburetor. These fed extra fuel to the carburetor bowls, thus keeping fuel volume up and temperatures down.

Vemp_0812_05_z 1978_greenwood_turbo_GT Alarm_system 5/13

The motion-sensor alarm system was located in a special housing on the roof's T-bar.

Willard also asked about the motion-sensor alarm system. Abshire hadn't even noticed it originally, but when prompted to describe the appearance of the car's T-roof bar, his description elicited a positive response.

Other items like the raised rear floor and Greenwood suspension were common to all three GTs, but even these small validations helped establish the car's provenance. LaEnvi also remembered that he had driven the car to Detroit one spring for an show, and he supplied Abshire with some photos taken there.

When Abshire contacted the car's former owners, he learned that it had been bought new in 1978 for $32,000, by a gentleman who owned an insurance company in the Northeast. He used the car lightly before sending it back to ACI in Sylvania, Ohio, for the addition of the Duntov headlights and a functional hatchback kit. In July 1988, the car was sold to the gentleman who owned the limousine service. It then sat in a garage for a number of years before being offered for sale online. As offered, the car had only 44,000 miles on the odometer.

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All Greenwood cars displayed an identifying plaque indicating the serial number.

Having confirmed that this was indeed the third Turbo GT, Abshire bought it (he won't say for how much). Rather than returning the car to original condition, he decided to leave the Duntov headlight treatment and the hatchback in place, since these were modifications performed by original builder ACI. But somewhere along the line, he does plan to repaint it in the original Burgundy color and refresh the upholstery. The engine bay will also be tidied up, and replacement center caps will be manufactured for the wheels.

As the car sits, its condition speaks well for the generally good care provided by the prior owners. In fact, the only things that were done to the Vette before Abshire's son arrived to pick it up were to install a new master cylinder and check over the brake system. Other than that, it started and ran well. For a low-volume, high-performance vintage tuner car, that's a rare thing indeed.

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Early advertising diagrams indicated how the Greenwood suspension would work.

The History Of The Greenwood Turbo GT
John and Burt Greenwood built quite a few race-based street cars in the '70s. Although they had developed their own unique Corvette suspension and aerodynamic systems to support their racing program, these technologies eventually found their way into production autos as part of an effort to offset their high tooling costs. Initially, the street cars were offered with minor aerodynamic improvements and exaggerated styling cues, but they quickly evolved into nothing short of high-speed endurance racers for the road.

Between 1975 and 1981, approximately 43 custom-made street cars based on five distinct body styles were produced under the umbrella of Greenwood International. These included the GT/Sebring GT (32 produced), the Sportwagon (1), the Turbo GT (3), the Daytona (5) and the GTO (2).

Vemp_0812_08_z 1978_greenwood_turbo_GT Fender_flare 8/13

The rear wing of the Turbo GT was made wider, to fit flush with the extended fenders.

In 1976, even as production of the Sebring GT continued, a prototype fastback coupe was being built to showcase Greenwood's growing expertise with turbochargers and the company's next generation of radical aerodynamics. Interestingly, this is the same time period when GM was exploring turbocharging as a serious option for the Corvette.

Greenwood chose a blow-through design-as opposed to a draw-through approach-to turbocharging because of its potential for superior performance, but serious developmental effort was required to make this fledgling technology work consistently and reliably. The second and third Turbo GTs reflected incremental design improvements, with the third one having an intricate fuel-management system added.

Vemp_0812_12_z 1978_greenwood_turbo_GT Rear_view 9/13

The '76 Turbo prototype featured more smoothly integrated fenders than the Sebring GT. The GT's short, vertical rear spoiler, meanwhile, gave way to an integrated wing. The notchback design was filled in and became a "fastback" with a large, nonopening rear glass window. The prototype was painted a two-tone silver-over-gray, similar to Greenwood's No. 77 "Batmobile" racer. Taller, sport-style mirrors were developed to aid in over-the-fender rear vision.

Vemp_0812_10_z 1978_greenwood_turbo_GT Hatch 10/13

A raised rear floor was required to accommodate the car's coilover suspension.

A few styling changes were adopted as the car neared production. The most significant arose out of the new glass hatchback of the '78 25th Anniversary model. The complications of the Sebring GT's fastback design were no longer an issue, so the rear wing was widened to fit flush with the extended fenders. It was also made thicker, with an upturned trailing edge to better manage airflow off of the new rear window.

The fenders were unchanged from the prototype and featured five vertical slots at the rear of the front panels to the new Turbo hood. A single NACA duct on the right side of the hood allowed additional cooling to the engine compartment.

The engine of choice was the L48 model due to its lower compression ratio. High boost pressures would cause detonation in the higher-compression L82, making the L48's stock 8.5:1 ratio a better choice. Still, it didn't resolve all the problems that arose when running a full 7 psi of boost. A water-injection system was devised to help alleviate the problem. Fed from the windshield-washer reservoir, this primitive charge-cooling setup could be considered the precursor to today's intercoolers.

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BFGoodrich ads from the period featured the Turbo GT prototype.

Other pieces and systems were custom-made to overcome the problems associated with the blow-through setup. A right-side exhaust manifold was cast to hold both the Air Research T04 Turbo and a wastegate fitted with an integral muffler. A crossover pipe connected the right manifold to the left, and a custom-bent pipe connected the turbo to the stock exhaust. A cast-aluminum bonnet fed by the turbo sat sealed atop a Holley 650-cfm carburetor that was specially prepared to handle the boost pressure.

To ensure adequate fuel delivery, two electric pumps took over the duties of the original single mechanical unit. The TH350 transmission was also tweaked to handle the extra power. But despite all the fortifications, problems persisted. The pressurized approach forced a lot of fuel into the combustion chamber, sometimes causing a "wash down" effect.

Vemp_0812_09_z 1978_greenwood_turbo_GT Rear_view 12/13

The suspension-a Greenwood specialty-didn't go unnoticed, either. Coilover shocks and heavy-duty sway bars out back were a given. The rear suspension also utilized unique upper and lower A-arm configurations, not unlike those of the C5. This radical (at the time) setup virtually eliminated the dive and squat associated with hard braking and acceleration.

The location of the suspension pieces, did, however, necessitate raising the part of the rear floor where the battery and storage bins resided. The new floor was cast in fiberglass and proved to be quite an exercise in fitment. The rest of the interior remained stock, except for a boost gauge neatly integrated into the dash. The serial plaques on the ashtray door and doorjamb indicated which of the three Turbo GTs you wer e riding in.

For more information on the Greenwood street cars, check out www.greenwoodcorvettes.com.

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