The 312 PB's origins lay in a 1970 regulatory change announced for the 1972 season. The FIA closed the loophole that had allowed cars like the Porsche 917 and Ferrari 512 to compete with engines up to 5.0 litres, raising the minimum weight of 3-litre prototypes to 650 kilograms. Porsche concluded the new rules did not suit their air-cooled 911-based engines and withdrew from factory prototype racing from 1972 to 1975. Ferrari, meanwhile, abandoned further development of the 512M and focused instead on a new platform.
The 312 PB was built around the Tipo 001 flat-12 engine from the 312B Formula 1 car, a water-cooled, four-valve-per-cylinder unit that shared the low centre of gravity philosophy of the flat-12 Porsche 917 but differed fundamentally in its water-cooling architecture. The engine had many design similarities to the F1 unit but was built largely from different, non-interchangeable parts — a distinction that would later create significant difficulties for owners of these cars in historic racing. Ferrari used 1971 as a test season to develop the package before committing to a full championship assault.
The car's competition debut at the 1971 1000 km of Buenos Aires was immediately marked by tragedy: Ignazio Giunti was killed when he hit Jean-Pierre Beltoise's Matra, which Beltoise was pushing back to the pits on the racing surface. The car did not win a race during the 1971 development season.
With Alfa Romeo as the only serious challenger in 1972, the 312 PB proved almost unbeatable. Ferrari won all World Sportscar Championship rounds it entered that season, securing the manufacturers' title. Enzo Ferrari elected to skip the 24 Hours of Le Mans, judging that the F1-derived engine could not last the full 24 hours of racing — a decision that protected the car's otherwise perfect seasonal record.
The 1973 season brought a more serious challenge from Matra, which had previously concentrated on Le Mans and now contested the full championship. Ferrari was compelled to enter the 1973 24 Hours of Le Mans despite lingering doubts about engine reliability over 24 hours. The team deployed one car as a "hare" to force the Matras into faster lap times and stress their reliability, while a second car ran the full distance. Ironically, only the "hare" Ferrari survived to the finish, coming second behind a Matra.
The 1973 season concluded with Matra winning the championship, reversing 1972's result. At the end of the season, Ferrari abandoned sports car racing entirely to concentrate on Formula 1, which had become the priority of its chief investor Fiat. The 312 PB's competition career was over.
The flat-12 engine's low centre of gravity gave the 312 PB excellent handling balance. However, the engine's complexity and its divergence from the F1 unit's parts meant that keeping cars running reliably in the long term was challenging. The fragility of the engine in sustained high-load running was a genuine concern throughout the car's career and was the reason Ferrari missed Le Mans in 1972.
The Ferrari 312 PB occupies an important place in sports prototype history as the car that dominated the 1972 World Championship for Makes and gave Ferrari its last manufacturers' title in sports car racing until the 499P era. Its brief but intense career — essentially just two full seasons — captured a transitional moment when flat-12 engines from Formula 1 were reshaping prototype design, and Ferrari's decision to withdraw at the end of 1973 left the car's potential partially unrealised.