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Volkswagen Air-cooled Flat Four (1954–1960) specs: 1.2L (72.7 ci) 4-cylinder, 77 x 64 mm (3.0315 x 2.5197 in) bore and stroke, 6.6:1 compression.
The Volkswagen Air-cooled Flat Four (1954–1960) is oversquare — the 3.0315" bore exceeds the 2.5197" stroke by 20.3% — 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 18.2 ci (298 cc).
6.6:1 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, sitting between the 69 ci and 96.6 ci members. 7 factory variants share these dimensions, rated from 36 to 40 hp across 1954–1960.
| Displacement | 72.7 ci / 1.2 L |
|---|---|
| Bore | 3.0315" |
| Stroke | 2.5197" |
| Cylinders | 4 |
| Compression ratio | 6.6:1 |
| Bore/stroke ratio | 1.203 |
| Block material | magnesium alloy |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 36–40 hp |
| Years | 1954–1960 |
| Bore/stroke character | 1.203 — 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 | 18.2 ci |
| Static compression | 6.6:1 — 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 |
|---|---|---|
| 1954 | 36 hp | — |
| 1955 | 36 hp | — |
| 1956 | 36 hp | — |
| 1957 | 36 hp | — |
| 1958 | 36 hp | — |
| 1959 | 36 hp | — |
| 1960 | 40 hp | — |
1 factory vehicle, 1960. Each year opens that model's engine table.