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Constructor Porsche AG
Chassis Steel bodyshell with reinforecements, added steel wheelarches. Front mounted 100liter fuel tank.
Body First steel, fiberglass doors, hood and engine cover.
Suspension McPherson strut at front, semi trailing arms at rear.
Gearbox Porsche Synchromesh 5 speed.
Wheelbase : 2413mm
Front track 1565mm
Rear track 1539mm
Engine Flat six cylinder, air-cooled. 2,8L and 3,0L. Fuel injection via high-butterflies, slides. Twin spark plugs.

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 focussed 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. One of the most legendary Porsches, the 911 Carrera RS 2.7, was born! 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. 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 accomodate them the arches were flared even more, giving the RSR 2.8 a very aggresive 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 Ferraris. 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. 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.

The Carrera RSR solidified the earlier successes of 911s in European rallies and major road races. The unprecedented success of the Porsche 971 during 1969-1972 limited the 911's racing sponsorship primarily in privateer hands. However, with the decline in interest in prototype racing and the 1974 demise of the CanAm series, suddenly production based cars such as the RSR were elevated to headline status and the factory went out of its way to assist customers. In 1973 Porsche quickly switched focus to the 3-liter European GT Championship (FIA Group 4). Porsche created the road legal Carrera RS by modifying the std 911 with a beefed up, lightweight engine, 917 brakes, adjustable shocks, wide body work and wheels, plus the signature whale tail spoiler. The RSR, strictly a race-car, had still a more powerful engine, coil over shocks, and even wider bodywork and wheels. 109 RSRs were built in 1974. Success was immediate. The RSR dominated the world GT scene from 1973 to 1975. Penske/Donahue selected the 1973 RS for the first IROC series in 1973. RSRs placed 5th thru 10th overall and first in GT class at LeMans in 1976. Throughout its lifetime, the 911 has been modified by private teams and by the factory itself for racing, rallying and other forms of automotive competition. It is among the most successful competition cars ever. In the mid 1970s, normally aspirated 911 Carrera RSRs won major world championship sports car races such as Targa Florio, Daytona, Sebring and Nürburgring, even against prototypes. The Porsche Carrera RS has been introduced in the US road racing scene in 1973. From that moment, it has become one of the most successful car ever. The first race of such a car was to happen at Daytona in 1973. This race was the first of the World Sportscar Championship and, there it faced true racing Prototypes as Matra, Mirage and Lola. Not still homologated in GT, the cars were forced to run against stronger machinery. Two brand new Carreras were entered by Brumos Racing and Penske Racing. These were RS cars because fitted with 2,7L engines.The drivers were Peter Gregg and Hurley Haywood on the Brumos car and Mark Donohue and George Follmer on the Penske car. After eight hours of grueling fight between the two sister cars and the retirement of every works car, the Brumos car took the lead of the race! Now the two cars were fighting for overall victory. The Brumos car eventually won the race and had set the Carrera's future in a significative way. From that moment, the Carrera began to dominate the series when introduced in IMSA racing. The first other team to acquire a Porsche Carrera RSR was Dave Helmick's and Gray Egerton's. The first car won at Sebring that year with Peter Gregg, Hurley Haywood and Dave Helmick at the wheel. The Porsche Carrera had won two of the greatest international races in its race debut. Fitted with a 2,8L F6 engine given for 300hp, the car was one of the most effective ones when in the hands of potent drivers. Its low fuel consumption coupled with a great reliability made this car a winner. The 1973 Porsche Carrera was the IMSA Champion with Peter Gregg that year. In 1974, a new version was born, this time the engine grew up to 3,0L. With a new tail section and an increase of power, such a car was nearly unbeatable. Furthermore, their number increased in a significant way. The IROC Series was no stranger to this fact. At the end of the 1973 season, a string of a dozen cars was left unused. These cars needed very few changes to adapt to the IMSA rules, and they found new owners very quickly. The 1974 season began with the cancellation of two of the longest events in the schedule. The Arab-Israeli war had put an embargo on the fuel and restrictions were made to long distance races. The season began thus at Road Atlanta with a 6Hour event. This first race was won by Al Holbert and Elliot Forbes Robinson. In fact, the Porsche Carreras won all but one event this year, clearly dominating the series. Peter Gregg emerged again as the series champion, as he proved his talent once again. This domination proved to become some kind of a threat to the series, as John Bishop sensed the fact that it would bore the crowds. The solution would be to bring new competitors to the German Make. It would take some time before the opposition would clearly materialize.
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