CLASSIC GR.3 - Bizzarrini GT 5300 Corsa 1965

Bizzarrini always had a keen sense for racing. Despite working for both Ferrari, then Lamborghini, and contributing to their best models, the 5300 was the first car fully credited to his name. Eventually, the very same companies he worked for would become key competition. As an underdog, Bizzarrini knew what he was up against, but he never stopped trying.

The 5300 project stems from a long and complicated relationship between Bizzarrini, Giugiaro at Bertone and Renzo Rivolta. These three worked together to create the Iso Rivolta 300, a flagship car for Iso, having a welded sheet steel monocoque and Corvette V8. Due to sporting nature of the chassis and the reliability of its American power, Bizzarrini wanted to go endurance racing, but Rivolta who owned Iso did not agree. Fortunately, by 1963, Rivolta was finally convinced to finance the development of a more sporting Iso Rivolta. The result was the precursor to the 5300 GT, the Iso Grifo.

The Grifo and 5300 where based on the Iso Rivolta 300 chassis. It was a welded sheet steel tub having a fully independent suspension by double wishbones in the front and a De Dion axle in the rear. These same characteristics were lent to the Grifo and 5300, albeit in a shorter chassis.

Unlike all Italian sports car tradition, Bizzarrini used an American engine for the 5300, specifically the Chevrolet V8. With this engine came a host of benefits: it was ample in power, cheap to purchase and maintain, simple to tune and best of it all, it would run reliably all day and all night. After moderate tuning, the engine provided 365 bhp, keeping it well ahead of Ferrari’s 275 GTB. Using lessons learned with the Ferrari 250 GTO, Bizzarrini pushed the heavy V8 far back into the engine bay as possible. When combined with the side-mounted gas tanks the weight balance of the 5300 was very close to a perfect, even during different fuel loads.

Bizzarrini offered the 5300 in two variations. As a strada, more interior appointments, including ventilation, were standard . For the racing client, or adventurous customer, Bizzarrini offered the competition version with a tighter steering ratio, hot engine, lightweight body and no seat belts! Over the years several changes were made to this Corsa version with some cars getting individual specification. For this reason, no two cars are exactly alike.

Highlighting the Corsa was a 405 horsepower (302 kw) version of the Corvette V8. The additional power was result of four twin choke side draught Webers mounted on a cross flow intake manifold. Other subtle engine modifications included polished ports, aggressive camshafts and a free-flow exhaust.

Thin gauge aluminum was used on all the competition cars. The body and other lightweight measures helped shed 110 lbs off the car.