What's the difference between a 911 2.0, 2.4, and 2.7 engine?

Understanding the Porsche 911 engine evolution is essential before buying any air-cooled car — the engine specification is the single largest driver of value variation within the same model year, and the mechanical injection cars behave very differently from the later CIS-injected or carbureted variants.

2.0-Litre (1965–1969)

The original 901-designated engine in carbureted form (Weber or Solex). Power ranged from 130 hp in the base 911 to 160 hp in the 911 S. The early S engines with Weber 40 IDS carburetors are the most driver-engaging; the 130 hp base engines are more forgiving. These are the most sonically pure air-cooled engines — higher revving, lighter. The downside: chain tensioner maintenance is critical on pre-1968 cars.

2.2-Litre (1970–1971)

The displacement bump added low-end torque and reduced the high-revving character slightly. The 2.2 T (carb), E (mechanical injection), and S (mechanical injection, 180 hp) are distinct variants. The 2.2 S is the sweet spot of this generation — high enough power to be genuinely quick, with the mechanical simplicity of the early cars.

2.4-Litre (1972–1973)

The 2.4 introduced oil filler cap relocation to the right rear quarter panel — the "oil filler behind the door" arrangement that is a 2.4 identifier. The 2.4 S produces 190 hp; the 2.4 E with Bosch mechanical injection is a refined touring engine. These cars benefit from Nikasil cylinder lining upgrades if not already done.

2.7-Litre (1974–1977) and the RS

The standard 2.7 used in the 911 base and S is an understressed touring engine — reliable and long-lived. The 2.7 Carrera RS engine (available 1973–1974) is categorically different: MFI, 210 hp, designed for motorsport homologation. A genuine RS engine in an RS-spec car trades at 300–500% premiums over a comparable 911 S. The CIS-injected 2.7 in post-1974 cars is adequate but lacks the character of the mechanical injection variants.