As it took shape, Projekt 1484 began to look quite a bit like the Monza GT. The Opel design was not mid-engined, nor was it in any way Corvair-based, but it shared many design cues with the Monza: a sloping nose with concealed headlamps, a low-slung fastback roofline, and a cropped Kamm tail with quad taillights.
We don’t know if MacKichan had been involved with the development of the XP-797 (it appears that the Monza SS and Monza GT were built after he left for Germany), but Bill Mitchell later confirmed that the Opel design was indeed based on the Monza GT, a design of which Mitchell was very fond. An additional connection was Tony Lapine, who joined MacKichan at Opel in 1964 and was involved in the sports car project’s subsequent development. (Interestingly, while Projekt 1484 did not share the Monza GT’s lift-up canopy, that feature reappeared on the 1969 Opel CD, a concept car based on the Diplomat 5,4.)
By 1965, Projekt 1484 had reached the full-size prototype stage. While it had found some support outside the styling department, principally from marketing executive Bob Lutz, senior Opel officials had little interest in pursuing the project even as an auto show confection. Opel’s philosophy at the time was that the company should show what it sold, and Opel was not in the sports car business.
In July 1965, Semon “Bunkie” Knudsen was promoted to group VP of GM’s Overseas and Canadian Group, following successful stints as general manager for Pontiac and Chevrolet. MacKichan had worked with Knudsen at Chevrolet and knew of his fondness for sporty cars. We assume that most GM executives were aware that Knudsen had revived the moribund Pontiac division with a new emphasis on performance. Suspecting that the sports car would be right up Knudsen’s alley, MacKichan and Lutz arranged for him to see the prototype. As expected, Knudsen loved it and gave his support for exhibiting the car on the auto show circuit.
The prototype made its public debut at the Frankfurt International Auto Show in October. Prosaically dubbed Opel Experimental GT, it was described as an aerodynamic test chassis for Opel’s new high-speed test track in Dudenhofen. Despite that cautious presentation, response was sensational. The car attracted hordes of curious showgoers and raised many eyebrows among the representatives of other automakers, who expected nothing more from Opel than bland porridge.
Seeing the enthusiastic reaction, Opel management reexamined the sports car project in a new light. There seemed to be a market for a production model. The question now was how to build it.
THE GT AND THE KADETT
Given the sports car’s likely volume — and the likely complexity of its body — Opel decided to outsource production of its body shell. Initial thoughts involved Karmann, but in early 1966, Opel officials met with representatives of the venerable French coachbuilder Brissonneau & Lotz, who had been trying unsuccessfully to pitch the idea of a Rekord convertible.
Brissonneau & Lotz were interested and signed a deal to produce tooling and bodywork for the prototypes. The actual stamping, welding, and body assembly would be subcontracted to the Parisian firm Chausson, best known today for its recreational vehicles. The Brissonneau & Lotz plant in northern France would handle paint, trim, and wiring before sending cars back to Opel’s Bochum plant for mechanical assembly.
There was little chance of any exotic hardware under the skin. Even if Opel management had been willing to make large investments in a relatively low-volume new product, selling price was a concern. Market research suggested that the sweet spot would be around 10,000 DM (about $2,500 at the contemporary exchange rate), where the new car would face little direct competition. At that price, a bespoke platform was out of the question. Instead, the sports car would share most of its mechanicals with the Kadett B.
The one major concession the stylists and engineers wanted was the location of the engine. The Kadett’s engine was normally mounted well forward in the interests of packaging efficiency, which was problematic with the sports car’s sloping nose. To preserve the prototype’s sleek profile, the styling team wanted to relocate the engine 15.75 inches (40 cm) farther back, but Opel’s cost accountants balked, seeing the engine relocation as an unnecessary expense.
Hoping to appeal to Teutonic pride of engineering, proponents insisted that the change would make a perceptible difference in the car’s handling and overall feel. To test that thesis, Hans Mersheimer authorized the construction of two test mules, one with the engine relocated, one without, and hired Porsche works driver Hans Hermann to test both at the Nürburgring. Predictably, Hermann’s professional opinion was that the car with the relocated engine felt better, so Opel management grudgingly conceded the point.
The running prototype shown to the press in 1967 had the 1,897 cc (116 cu. in.) version of Opel’s new cam-in-head (CIH) engine, recently introduced on the Rekord. In the prototype, the engine used an experimental 4V Solex carburetor and a modified head with 10.0 compression, giving a net output of 128 PS DIN (126 hp, 94 kW) and 115 lb-ft (156 N-m) of torque. Since the prototype weighed less than a ton and was quite slippery aerodynamically, it had excellent performance and a claimed top speed of 130 mph (210 km/h). It looked very promising.
THE PRODUCTION OPEL GT
Clare MacKichan departed long before Opel’s new sports car went into production. In 1967, he returned to the U.S. to become director of advanced styling, turning over the reins at Opel to Chuck Jordan, who had spent the previous five years as GM’s director of exterior design. Jordan would oversee final development of the production sports car, now known simply as Opel GT.
Inevitably, the GT’s shape underwent many changes between prototype and finished product, emerging taller, thicker of snout and plumper of hindquarters, with a more sharply cropped tail, a prominent hood bulge, and a pair of cooling slits atop the nose. Some of the changes were undoubtedly driven by production necessity, others by regulatory requirements (the prototype’s rectangular pop-up headlights would not have been legal in the U.S.), while others were dictated by wind tunnel testing. In production trim, the GT had a drag coefficient of 0.39: not great by today’s standards, but first rank for the late 1960s and significantly better than the C3 Corvette, to which the Opel was now taking on a decided and probably non-coincidental resemblance.