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Volvo B20B specs: 121 ci 4-cylinder, 88.9 x 80 mm (3.5000 x 3.1496 in) bore and stroke, 9.3:1 compression. Rated 118 hp, 1969. Used in the Volvo P1800.
The Volvo B20B is oversquare — the 3.5" bore exceeds the 3.1496" stroke by 11.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.1496" stroke does not reach 4,000 ft/min of mean piston speed until about 7,600 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 30.3 ci (496 cc).
9.3:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Volvo 121ci family, all of them 121 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 121 ci |
|---|---|
| Bore | 3.5" |
| Stroke | 3.1496" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9.3:1 |
| Bore/stroke ratio | 1.111 |
| Fuel type | gas |
|---|---|
| Advertised HP | 118 hp |
| Years | 1969 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1969 | B20B gross | 118 @ 5800 | 123 lb-ft @ 3500 | 9.3:1 |
Factory specification sheet.
| Bore/stroke character | 1.111 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,150 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.3 ci |
| Static compression | 9.3:1 — low by modern standards, generally happy on regular pump fuel |
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1 factory vehicle, 1969. Each year opens that model's engine table.