Rule changes at the end of the 1972 season left the Porsche 917 obsolete for the World Sportscar Championship. Building a completely new car to campaign in the prototype class, which now counted for the World Championship was not a really an option. These prototypes were basically Formula 1 racers with a two seater body and the only serious competitors were existing F1 teams like Ferrari and Matra, and British teams using the Ford Cosworth DFV engine. With no recent F1 experience, it would have been too much of an effort to build a competitive prototype racer for Porsche.
Fortunately for Porsche a new European GT Championship was created, for which Porsche’s 911 model was eligible, so Porsches European motorsport activities for 1973 were focused on the Group 4 GT class. Competition would come from Porsche’s perpetual nemesis, Ferrari, in the form of the 365 GTB Daytona ’Competizione’. With a displacement which was almost twice that of the largest Porsche 911 engine at the time, the Daytona was the clear favourite. Work was started on a production 911, that could form the base for a racer quick enough to take on the Ferrari.
Chosen as base for the new car was the Porsche 911 S, that had been successful in events like the Rally Monte Carlo and the Tour de France. Main design focus was to save weight and increase the output of the flat 6 engine. The bore of the 2.4 litre engine was increased by 6 mm to 90 mm and with it the output of the now 2.7 litre engine grew with 20 bhp to 210 bhp. To get the added power on the road, Porsche fitted wider rear than front tires on a roadcar for the first time in its history. A lot of weight was saved by stripping the 911 of all luxuries and the use of fiberglass and thin gauge steel for various bodyparts.
Carrera RSR 2.7
To be homologated for the Group 4 class, at least 500 examples of the model had to be constructed. Production of the RS 2.7 started in 1972 and its stunning performance made it an immediate hit. More than enough cars were constructed, securing the Porsche’s entry in the 1973 GT Championship. The rules allowed for some modifications to be made to the racing cars compared to the road cars. Most obvious difference between the Carrera RS 2.7 and its racing counterpart, the Carrera RSR 2.8 was the slight displacement increase.
Carrera RSR 2.8
The engine was bored out even more to 92 mm which resulted in a displacement of 2.8 litres. The compression ratio was raised to 10.5 : 1 and together with the displacement increase it resulted in a stunning leap of power of almost 100 bhp. Even wider rear wheels were fitted and to accommodate them the arches were flared even more, giving the RSR 2.8 a very aggressive stance. Porsche 917 derived vented and cross drilled discs replaced stock brakes to ensure that the fastest 911 to date stopped as quick as it went.
At its racing debut at the 1973 Daytona 24 Hours, the 911 Carrera RSR 2.8 immediately proved to be the car to beat that season. After the 3-litre prototype racers retired Peter Gregg and Hurley Haywood took the overall victory, beating the 7 litre Corvettes and 4.4 litre Ferrari s. Further success was had at the Sebring 12 Hours and the Targa Florio of the same year. In the European GT Championship, where the RSR 2.8 was originally designed for, it was almost unbeatable, winning six of the nine rounds and the championship.
Carrera RSR 3.0
Throughout the season, Porsche campaigned a ’prototype’ version of the 2.8, which featured further modifications that no longer made it eligible for the Group 4 class. These modifications were fitted to a new series of road cars, the 3 litre Carrera RS 3.0, making the RSR 3.0 eligible to race in 1974. The new car continued the 2.8’s dominance in the Group 4 class and so did its replacement, the turbocharged 934 of 1976.
Featured in the first shot is the actual Targa Florio winning RSR. Originally piloted by Gijs van Lennep and Herbert Muller, the winner is owned by the Porsche museum and is seen here at the 2002 Goodwood Festival of Speed. The next car is pictured on the LeMans track on the occasion of the 2002 LeMans Classic. Featured in the last three shots are three RSRs taking part in the 2003 Tour Auto, one of the few events the RSR did not win in 1973.