Casa dell’Auto Marinella Testadoro

The Giusti Marinella Testadoro was a limited-production Italian racing car developed in 1948 by Casa dell’Auto, a Turin-based constructor founded by Giorgio Giusti. The model represented the culmination of Giusti’s postwar development program following earlier Testadoro Sport and Drin Drin variants, with the objective of producing a fully integrated competition car rather than a modified production-based special. The Marinella was conceived as a complete racing automobile combining advanced engine design, a purpose-built chassis, and specialized coachwork, reflecting the rapid technical evolution of small-displacement sports racing in Italy during the late 1940s. The power unit was designed by engineer Arnaldo Roselli, known for the Testadoro cylinder head developed for Fiat 500 Topolino-based competition engines. The Marinella employed an inline four-cylinder engine of 742 cc displacement, fitted with a lightweight aluminum alloy cylinder head featuring hemispherical combustion chambers and radially arranged valves. This configuration improved breathing efficiency and permitted higher engine speeds relative to standard Topolino units. The engine developed approximately 45 horsepower at 6,500 rpm and was coupled to a five-speed manual gearbox, an advanced feature for the class that allowed closer ratio spacing and improved exploitation of the narrow power band. Dissatisfied with the limitations of the Fiat Topolino chassis used in earlier cars, Giusti commissioned Gilberto Colombo to design a dedicated structure. Colombo, founder of Gilco, had previously designed the tubular frame of the first Ferrari 125 S and was a leading proponent of lightweight spaceframe construction. For the Marinella, he created an exclusive “Isorigid” chassis, a registered Gilco concept, consisting of small-diameter steel tubes arranged in a fully triangulated lattice derived from Grand Prix practice. This structure offered markedly higher torsional rigidity than conventional ladder frames and was distinct from Gilco’s standard 750-class chassis types. Suspension design reflected the same advanced approach, with independent front double wishbones and coil springs, contrasting with the transverse leaf spring layouts still common among competitors. The bodywork was executed by Carrozzeria Zagato in a “siluro” configuration typical of contemporary sports-racing cars. The aluminum body featured a narrow frontal area, open wheels, and a streamlined profile closely following the chassis contours, with multiple air intakes incorporated to address cooling requirements. The aerodynamic emphasis aligned with the car’s lightweight philosophy and small-displacement performance strategy. Production is generally cited as nine examples, making the Marinella one of the more widely available ready-to-race cars in the 750 cc category. The model competed in regional and national Italian events, where Giorgio Giusti himself achieved notable results, including overall victory in the Coppa Michelin at the Valentino circuit in Turin, frequently outperforming larger-displacement but technically less advanced rivals.