The 312 PB emerged from a significant shift in international sports car regulations announced in 1970, to take effect in 1972. The existing loophole that had permitted large-displacement homologation specials — cars such as the Porsche 917, Ferrari 512, Ford GT40, and Lola T70 running engines of up to five litres — was closed. Minimum weight for three-litre prototypes was raised to 650 kg. Porsche, whose 908/03 weighed approximately 100 kg less than that limit, deemed the new formula commercially unattractive and withdrew from World Championship sportscar racing from 1972 to 1975. Ferrari's own 512S had spent much of 1970 losing to the Porsche 917, and after updating it to the 512M specification late that year, the company abandoned further development of that car entirely.
Ferrari used 1971 as a test season to develop an entirely new approach. The 312 PB was built around the Tipo 001 flat-12 "Boxer" engine derived from the 312B Formula One car. The layout shared a philosophical similarity with the flat-12 Porsche 917 in its low centre of gravity, but Ferrari's unit used water-cooling and four-valve cylinder heads. Despite the shared lineage with the F1 engine, the 312 PB's power unit shared almost no interchangeable parts with its Formula One counterpart — a fact that has made sourcing components a persistent challenge for owners racing the cars in historic competition.
The 312 PB made its race debut at the 1971 1000 km of Buenos Aires, driven by Ignazio Giunti and Arturo Merzario. The event began in tragedy when Giunti was killed after striking Jean-Pierre Beltoise's Matra, which was being pushed back to the pits by the French driver on the racing surface. The car did not win during the 1971 test season, while Alfa Romeo, competing with the 33/3, took three World Championship victories.
In 1972, with Alfa Romeo as effectively the only serious competition, the 312 PB was in a class of its own. Ferrari entered the car in every round of the World Sportscar Championship and won each race the team contested. One notable exception was Le Mans: Ferrari chose not to enter, judging that the F1-derived engine had shown itself incapable of lasting the 24-hour distance during testing, and preferring not to damage what would otherwise be a perfect record.
The 1973 season brought greater difficulty. Matra, which had previously concentrated its efforts on Le Mans, entered the full championship while Alfa Romeo was absent. The French manufacturer won multiple rounds, pushing Ferrari into second in the championship standings. Ferrari responded to the Le Mans challenge by entering the 1973 24 Hours with an improved but still uncertain engine. The team deployed a tactical "hare" car intended to pressure the Matras into driving at an unsustainable pace. Ironically, the hare was the only Ferrari to reach the finish, crossing the line in second place behind a Matra. The Targa Florio also proved difficult: despite the absence of Matra from that race, neither Ferrari nor Alfa finished, and a privateer Porsche 911 Carrera RSR — which had qualified fifth — took an unexpected victory.
At the end of 1973, Ferrari withdrew from prototype sports car racing to concentrate fully on Formula One, where the team had struggled sufficiently that it had missed several Grands Prix that season.
The 312 PB represents one of the most successful single-season sports car campaigns in the history of the World Sportscar Championship, with its unbeaten 1972 record standing as a high-water mark of Ferrari's endurance racing programme of the early 1970s. Its flat-12 engine architecture, sharing conceptual roots with the company's Formula One design philosophy, made it a technically significant machine at the intersection of Ferrari's two primary competitive disciplines of the era.