When, in 1977, Porsche factory added to its range of products, in which there was the 924, the 928, it was clear that it was necessary to limit the range of the 911/930. So the "serie L" was launched. In the effort to standardise the production, the 911 Carrera 3.0 and the 911 2.7 were replaced with a unique model, which combined the body (with large rear mudguards) and the rear-part of the 3 litres Carrera, with a 3 litres engine very similar to the 3.3 litres engine of the Turbo. Even in this case it was necessary to add an air pump to respect the new European rules against pollution (this pump is set in action by a V-shaped belt which is connected with the hub of the air-cooling fan). In comparison with the 3 litres engine, the flat-six of the 911 SC is a little less powerful: 180 hp. (132 kw) @ 5500 rpm. Maximum torque: 27 kgm. @ 4100 rpm. This result has been reached using the camshaft of the Carrera 3.0, whom angle timing has been anticipated with 6° than the rotation of the engine shaft. These are timing angles:

The engines for the USA an Japan, had the valve gear of the Carrera 3.0. The overheads, (except the opening which takes the air in the exhaust pipe), the dimensions of the valves, of the ignition pipes, the compression ratio, are the same of the Carrera 3.0. The engine of the 911 SC, type 930/03 (type 930/13 for the Sportmatic version) uses the same engine block of the 3.3 litres turbocharged engine, with 7 main bearings of 60 mm of diameter, and another one, with 31 mm. diameter, which is between the distribution gear and the pulley which operates the air-cooling fan. In spite of bore and stroke are the same of the Carrera 3.0, the engine shaft of the 911 SC, is completely different. Its mechanical drawing and balancing are very similar to the whom of the 3.3 litres engine. But the crank pins haven't the same dimensions, so the width of the overheads has been reduced by 1,2 mm. (width: 22,6 mm); the diameter is 53 mm. As in the Turbo, the ignition is electronic without contact-breaker. It's the first time that such a system is assembled on a car without a turbocharger. This car has the air cooling fan with 11 blades, more efficacious than the one with 5 blends with the same diameter (226 mm.) but with the same rotation.