Ferrari 312 PB
Ferrari's flat-12 prototype that dominated the 1972 World Sportscar Championship.
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The Ferrari 312 PB began life in 1971 as a Group 6 prototype, though it was officially called the 312 P. The extra "B" was added by the motorsports press to tell it apart from an earlier Ferrari model with the same name. It belonged to the Ferrari P series of prototype sports cars, but for 1972 it was reclassified as a Group 5 sports car.
Development
Ferrari built the car after a rule change for 1972 closed the loophole that had allowed 5-litre engines in sports cars like the Porsche 917 and Ferrari 512, provided at least 25 were made. The minimum weight for 3-litre prototypes was raised to 650 kg. Porsche decided the new weight was too much—their 908/03 was 100 kg lighter—and their air-cooled two-valve engine only produced 370 hp, so they would have needed a new normally aspirated engine. Instead, Porsche focused on the 911, Can-Am, and turbocharging, selling their 908s to customers who had to add ballast.
The factory sat out world championship sports car races from 1972 to 1975. Matra and Alfa Romeo were willing to compete, but only in some seasons or events. Ford’s Cosworth-V8, successful in Formula 1, was available for independent builders, but vibrations made it unreliable for endurance racing, as the 1968 Ford P68 had shown.
After the 512S was mostly beaten by the Porsche 917 in 1970, Ferrari modified it into the 917K-like 512M late that season, then dropped further development and left all 512s to customer teams like Penske Racing, NART, and privateers. Instead, Ferrari used 1971 as a test season for a new 3.0-litre prototype based on the Tipo 001 flat-12 "Boxer" engine from the 312B Formula 1 car. The design was similar to the flat-12 Porsche 917 layout, with a low centre of gravity, but Ferrari used water-cooling and four-valve heads.
The car showed promise but did not win, while the similar Alfa Romeo 33/3 V8 took three world championship wins against the dominant Porsche 917 and 908. The 312 PB’s engine shares many design ideas with the F1 engine, but nearly every part is different and cannot be swapped. This has made spare parts for the fragile engine very hard to find for historic racing, compared to the F1 flat-12.
Racing history
The car first appeared at the 1971 1000 km of Buenos Aires, driven by Ignazio Giunti and Arturo Merzario.
Lore & Background
The 312 PB was developed after a 1970 regulation change closed the loophole for larger-engined sports cars, raising the minimum weight of 3-litre prototypes to 650 kg. Ferrari abandoned further development of the 512M and focused on a new 3.0L prototype based on the Tipo 001 flat-12 engine from the 312B Formula 1 car. The engine used water-cooling and 4-valve heads, similar in layout to the Porsche 917 flat-12 but with nearly every part different and non-interchangeable with the F1 flat 12, making spare parts difficult to obtain for historic racing.
The car first appeared at the 1971 1000 km of Buenos Aires, driven by Ignazio Giunti and Arturo Merzario. Its history started tragically when Giunti was killed in that race after hitting Jean-Pierre Beltoise's Matra head-on. The 312 PB did not win a race in 1971. In 1972, with only Alfa Romeo competing, the 312 PB won all World Sportscar Championship races it entered, though Ferrari skipped Le Mans because the F1-based engine had not lasted 24 hours in testing.
In 1973, Matra challenged for the championship while Alfa was absent. Ferrari entered the 1973 24 Hours of Le Mans with an improved yet still doubtful engine, using one car as a 'hare' to lure Matras into faster laps. Only the 'hare' Ferrari survived 24 hours, finishing second behind a Matra.
The championship saw the same order, with two Italian wins to five French. At the Targa Florio, the 312 PB could not defend its 1972 win as proper sports prototypes failed and a modified Porsche 911 Carrera RSR won. At the end of 1973, Ferrari abandoned sports car racing to focus on Formula 1.
Reader's Guide
The Ferrari 312 PB is notable as the car that achieved a perfect World Sportscar Championship season in 1972, winning every race it entered. Its development reflected a strategic shift by Ferrari after the 512S was beaten by the Porsche 917, leading to a new prototype based on Formula 1 technology. The flat-12 engine, while similar to the Porsche 917's layout, was water-cooled and used four-valve heads, but its fragility and parts scarcity have made it challenging for historic racing. The car's tragic debut at Buenos Aires in 1971, where Ignazio Giunti was killed, marked a somber start.
Despite skipping Le Mans in 1972 due to reliability concerns, the 312 PB's dominance that year stands as a high point. In 1973, it faced stronger competition from Matra and could not repeat its success, finishing second at Le Mans and in the championship. Ferrari's withdrawal from sports car racing at the end of 1973 ended the 312 PB's career, but its record of a full championship sweep remains a significant achievement in the World Sportscar Championship.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Ferrari 312 PB (CC BY-SA 4.0).
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