History of the 1969 - 1971 Porsche 911
The Porsche 911 was well-established by 1969, and the new B-Series improved it in several ways. The wheelbase was extended 2.24 inches, through lengthened trailing arms, though the engine and transmission stayed in the same place. That changed the weight balance from 41.5/58.5 to 43/57, and both handling and ride improved. The troublesome Nadella half-shafts were replaced by Lobro units with constant velocity joints, and the shafts turned rearward from inner to outer joints. Two 6-volt batteries replaced the single 12-volt unit, one behind each headlight.
Porsche avoided American emissions issues with Bosch fuel injection in the 911S and new 911E mid-range models. It was driven off the camshaft by a cogged belt with a hand-throttle to increase revs for a cold start. The fuel injection boosted the 911S to 190 bhp and the 911E to 158bhp, but care had to be taken not to pump fuel before starting or the resulting backfire would blow the air box apart. The 911E was also fitted with Boge self-levelling front struts, but they tended to leaked and presumably all have been replaced by now. The leaky plastic "soft" window at the rear of the Targa was replaced with glass.
A step backwards was changing the aluminium crankcase to magnesium. It saved 22 lbs, but put three metals with differing expansion rates in close contact. As a result the head studs would pull out, but all should have been replaced with diavel by now. The 911S received a 5-speed transmission and it was optional on the 911E. The Sportomatic was an extra-cost option and never popular.
The C-Series of 1970 received a boost in engine size from 1,991cc to 2,185cc and the clutch mechanism was improved. Changes were few to the 1971 D-Series, though the Boge self-levelling shocks were abandoned and the Sportomatic transmission was no longer available on the 911S. The 5-speed gearbox was redesigned for 1972's E-Series, in a traditional pattern, without the "dog-leg" first. A new front spoiler was added which vastly improved stability at high speeds.
One short-lived idea proved disastrous, when the dry sump oil reservoir was moved from behind the rear wheel to in front, with a filler door that opened from outside. Unfortunately, the uninitiated occasionally assumed this was the petrol filler.
The company worried how to sell 500 copies to enter production racing, but their fears were unfounded. The Carrera RS was launched at the Paris Salon in October 1972 as a 1973 model in both lightweight and Touring forms. All 500 cars were sold in a week and total production would reach almost 1,800, meaning the Carrera RS could not only compete in Class 4, but also in the less-competitive Class 3, where it would clean up.