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Volkswagen Air-cooled Flat Four (1950–1953) specs: 1.1L (69 ci) 4-cylinder, 75 x 64 mm (2.9528 x 2.5197 in) bore and stroke, 5.8:1 compression.
The Volkswagen Air-cooled Flat Four (1950–1953) is oversquare — the 2.9528" bore exceeds the 2.5197" stroke by 17.2% — a layout that favors airflow and RPM over leverage at the crank. The 2.5197" stroke does not reach 4,000 ft/min of mean piston speed until about 9,500 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 17.3 ci (283 cc).
5.8:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 28 engines in the Air-cooled Flat Four family, the smallest at 69 ci. 4 factory variants share these dimensions across 1950–1953.
| Displacement | 69 ci / 1.1 L |
|---|---|
| Bore | 2.9528" |
| Stroke | 2.5197" |
| Cylinders | 4 |
| Compression ratio | 5.8:1 |
| Bore/stroke ratio | 1.172 |
| Block material | magnesium alloy |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Years | 1950–1953 |
| Bore/stroke character | 1.172 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,520 ft/min — conservative for a street engine |
| Displacement per cylinder | 17.3 ci |
| Static compression | 5.8:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1950 | — | — |
| 1951 | — | — |
| 1952 | — | — |
| 1953 | — | — |
1 factory vehicle, 1950–1953. Each year opens that model's engine table.