The first editions of the 911 had a rear-mounted 130 PS (96 kW; 130 hp) Type 901/01 flat-six air-cooled engine displacing 1,991 cc (2.0 L) compared with the 356's four-cylinder, 1,582 cc (1.6 L) unit.
Production of the 356 ended in 1965, but there was still a market for a 4-cylinder car, particularly in the US (The Porsche 912, introduced in the same year, served as a direct replacement, offering the de-tuned version of 356 SC's 4-cylinder, 1,582 cc (1.6 L), 90 hp (67 kW; 91 PS) boxer four Type 616/36 engine inside the 911 bodywork with Type 901 four-speed manual transmission (a 5-speed manual transmission was optional).
The E series for 1972–1973 model years (August 1971 to July 1972 production) had a new, larger 2,341 cc (2.3 L) engine. This is known as the "2.4 L" engine, despite its displacement being closer to 2.3 litres. The 911E (Type 911/52 engine) and 911S (Type 911/53) used Bosch mechanical fuel injection (MFI) in all markets. With power and torque increase, the 2.4-litre cars also got a newer, stronger transmission, identified by its Porsche type number 915.