The construction of these two cars was a result of certain regulations established by the CSI (Commission Sportive Internationale, predecessor of the current FIA) in 1968 when it formed the Sport class for cars with a maximum of five liters, produced in 50 then 25 units. Porsche went to work straight away, and on 21 April 1969, 25 917s were submitted to the CSI emissaries for approval in the courtyard of the German marque's factory.

1969 was a critical year for both Porsche and Ferrari. Porsche hit the track with the car that would eventually give it a first win at Le Mans, and Ferrari secured its future. The arrival of Fiat provided Enzo Ferrari an ideal situation: he benefitted from the financial support given by the large industrial group all while maintaining his independence. As the Porsche 917 made its debut at the 24 Hours and in the World Marques Championship, Ferrari launched the research and development, and construction of the 512 S. The German manufacturer's 917 was distinct for its chassis, a structure of small aluminum tubes weighing less than fifty kilos. Its air-cooled engine was Porsche's first 12-cylinder motor. For the 512 to be ready for the start of the 1970 season despite strikes in Italy that had disrupted the car's construction, Ferrari opted for tried and true rather than innovation. Still, the Italian manufacturer clinched its first victory in only its second race, at the 12 Hours of Sebring, thanks to Mario Andretti, Ignazio Giunti and Nino Vaccarella.

Early in the 1970 season, a certain balance had settled in between the top speed linked to the aerodynamic efficiency of the 917 and the 512 S's maneuverability in winding sections of the circuit, thus heralding a highly anticipated duel at the 24 Hours of Le Mans.

The 38th running of the race was marked by terrible weather and a string of retirements. Of Ferrari's four official 512 Ss, only the one shared by Jacky Ickx-Peter Schetty was still racing after four hours. Problems with the Porsche 917s allowed the Belgian driver and Swiss driver to climb to second position, but then Ickx left the track at 01:35 on Sunday. Even before the mid-race point, there remained only one factory Ferrari on the track.

The seven 917s that had taken the start were not spared either: five retired with engine troubles: (Rodríguez-Kinnunen, Elford-Ahrens, Siffert-Redman), incident (Hailwood-Hobbs) and flat tyre (Piper-van Lennep). At the chequered flag, the two remaining 917s finished in the top two spots, with in order Richard Attwood-Hans Herrmann and Willi Kauhsen-Gérard Larrousse.

Ferrari finished in fourth and fifth places with the 512 Ss of Ronnie Bucknum-Sam Posey (North American Racing Team) and Hugues de Fierlant-Alistair Walker (Ecurie Francorchamps). In 1971, the Porsche 917 scored its second win in a row as well as a new distance record (thanks to Helmut Marko-Gijs van Lennep) against the Ferrari 512s fielded by partner teams. Factory Ferrari prototypes would not be seen again at the 24 Hours until 1973.

PHOTOS (Copyright - ACO/ARCHIVES): LE MANS (SARTHE, FRANCE), CIRCUIT DES 24 HEURES, 24 HOURS OF LE MANS, 13-14 JUNE 1970. Above: Richard Attwood and Hans Herrmann gave Porsche its first win at the race, 19 years after the German marque's first participation. Below: the 512 S of Alistair Walker and Hugues de Fierlant was one of two Ferraris to cross the finish line.