Instead, in 1971, Ferrari focused on a new 3.0L prototype based on the 180° flat-12 "boxer" from the 312B F1 car. Officially this design was known as 312P, the motorsports press appending the B to avoid confusion with the earlier 312P V12 cars. This design was similar to the traditional Porsche engine layout with its low center of gravity, but Ferrari used water-cooling and 4-valve heads. The car was promising, but did not win, while the similar Alfa Romeo 33 scored two wins against Porsche's dominance. The 312PB's engine has many similarities in design to the F1 engine, but nearly every part is different and non-interchangeable with the F1 flat 12. This has led to problems for users of these cars in historic racing, as spare parts for these quite fragile engines, are, in comparison to the F1 flat 12 engine, very difficult to obtain.