www.QV500.com - Porsche 911 (1974 - 77) Part 7: 911 3.0 Carrera RSR
 
For the 1974 season, Porsche produced yet another evolution of the 911. Developed around the 3-litre RS homologation special, the 3-litre RSR became the most successful Group 4 car of its era. It was the last normally-aspirated 911 racer for two decades, subsequent variants being based on the turbocharged 930. Despite a prodigious rise in output though, later turbocharged 911's were not only heavier but a good deal more complex, this allowing the 3-litre RSR to remain competitive for nigh on a decade. In its early years, the RSR swept all before it in IMSA, Trans Am and the FIA World Championship, production beginning in late 1973.
   

They were equipped with hot Typ 911/75 engines featuring high-lift camshafts, Bosch slide injection and twin plug ignition. There was also a large capacity dry sump oil tank and dual megaphone exhaust from the 2.8 RSR. Displacement remained unchanged from the RS at 2992cc but the compression was upped from 9.8 to 10:3.1, the result having been 330bhp at 8000rpm. The five-speed transmission from the RS was installed along with a new dry plate Fichtel and Sachs sintered clutch. Coil springs were either steel or titanium. Visually the 3-litre RSR was enhanced with special five-spoke centre-locking 15-inch wheels, these having been 10.5-inches wide at the front and a massive 14-inches at the back. Ultra-light glassfibre panels were used for the ventilated wheelarch extensions, bumpers, front lid, engine cover and rear spoiler. Inside, the stripped-out cockpit got a solitary high-backed Recaro bucket seat with vinyl bolsters and clotch centre, a six-point racing harness holding the occupant firmly in place. Weighing in at a mere 900kg, the RSR was obviously a very quick car, in excess of 170mph having been possible whilst 0-60 took less than five seconds. Towards the end of 1974, most cars were coming out of the factory with closer to 350bhp, the last dozen examples (made from mid 1974) having been built on the 1975 model year H-series platform. Consequently, these cars use a 560 as opposed to a 460 VIN prefix. Some later cars were also equipped with the Carrera Turbo-style flat front bumper first used by Peter Gregg and the Brumos team. The RSR raced through the 1974 and ’75 seasons vanquishing the opposition and providing Porsche with its most successful customer racing car.