312 PB
In 1971, another rule change was announced for 1972, and Ferrari abandoned further development of the 512 in order to focus on a new 3 Litre prototype based on the F1 car. The 312PB would prove fast but fragile in its debut at the 1971 Sebring 12 hours. Further development over the 1971 season brought reliability, with the speed.
In 1972, the 312PBs with the flat boxer engine was very successful and won all races of the World Championship for Makes in which it competed. Ferrari didn't enter the 24 Hours of Le Mans in 1972, as Enzo Ferrari thought that the F1-based engine could not last the full 24 hours. He would be proven wrong.
They had to enter Le Mans in 1973, though, and finished second behind Matra, same as in the championship. At the end of the 1973 season, Ferrari forced to abandoned sports car racing, by FIAT, and ordered to focus on F1.
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