Porsche had already used the 3.0 ( Turbo ) engine without the turbo-charger in the 1975 Carrera 3.0, but in 1977 the 2.7 engine was definitely put aside. The new SC used the 3.0 litre unit, because it had better reliability and more potential for future tuning than the 2.7 engine.
Had all the previous years a choice of different 911 models been available, in 1978 only two models were available: the SC and the Turbo.
What 'SC' actually stands for is still a point of discusion, but Super Carrera sounds reasonable to me.
The SC was even more luxurious then the Carrera 3.0 of the years before. The engine however didn't deliver as much power as the Carrera 3.0's engine ( 20 bhp less ), but because more torque was available at lower revs the car was nicer to drive. A new Sport Group package option added the well-known waletail and front air dam. The black Fuchs wheels were also part of this package. Also optional were red and blue 'Martini'-stripes, refering to the victories of the Porsche racing cars ( option M42 ).The sportomatic option was finally dropped. The standard cars had ATS wheels ( 6Jx15 ) and were delivered with the 'black-look', although some models were delivered with chrome parts, like the one in the picture above. I think this was optional, but I can't find evidence of that. Anybody knows?
Because of all the luxury the 911 gained some more weigth and now tipped the scales at 1160 kg's.
Porsche made plans to replace the 911 with the 928, but the 911 SC still sold 50% better than the 928 and therefore Porsche revised it's strategy and decided to inject new life into the 911. In 1980 all models except the ones for the american market ( enviromental laws ) gained power and now delivered 204 bhp. The same year the 911 was offered in America as a limited edition model 'The weissach Edition 911', seen in the picture above. This model featured special paint, a leather interior and a 'wale-tail', other features were comparable with the Sport Group package. The wheels were painted 'platinum' metallic on all 'weissach' models.
In 1981 a concept car was presented at the Frankfurt motorshow. This concept car was a cabriolet version of the 911 and featured four-wheel drive. In 1982 the 911 SC cabriolet went on sale ( the first cabriolet since the 356 ).The cabriolet was based on the Targa's bodywork and was said to need very little extra reinforcements. Since it's introduction the cabriolet slowly gained market share at the expense of the Targa.
The SC had some minor changes during the period it was sold. In1980, the same year the power was increased to 204 bhp, side-indicators were added behind the front wheel. That year the 911 was equiped with a controversial black and white 'checker' interior. In 1981 the spoiler for the 'Sport'-version was modified ( the Weissach-version in the image above still has the older model ). The air-inlet grille was now the same as on the 'Turbo' running across the whole length of the spolier. The room beneath the spoiler was still bigger than on the Turbo's spoiler. In 1982 this design was no longer used and the 'Sport'-version got the Turbo's spoiler as seen on this 1982 model. The silver rim of the Fuchs wheels was now polished (also in this image).