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Volvo B18B specs: 109 ci 4-cylinder, 84.1 x 80 mm (3.3126 x 3.1496 in) bore and stroke, 10:1 compression. Rated 100-115 hp, 1961–1968.
The Volvo B18B is oversquare — the 3.3126" bore exceeds the 3.1496" stroke by 5.2% — 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 27.3 ci (447 cc).
10:1 is in the range that usually runs on pump premium.
It is one of 2 engines in the Volvo 109ci family, all of them 109 ci — the differences between them are in compression, heads and rating, not displacement. 8 factory variants share these dimensions, rated from 100 to 115 hp across 1961–1968.
| Displacement | 109 ci |
|---|---|
| Bore | 3.3126" |
| Stroke | 3.1496" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.052 |
| Fuel type | gas |
|---|---|
| Advertised HP | 100–115 hp |
| Years | 1961–1968 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1965 | B18B gross | 108 @ 5800 | 110 lb-ft @ 4000 | 10:1 |
Factory specification sheet.
| Bore/stroke character | 1.052 — 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 | 27.3 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| 1961 | 100 hp | B18B |
| 1962 | 100 hp | B18B |
| 1963 | 100 hp | B18B |
| 1964 | 108 hp | B18B |
| 1965 | 108 hp | B18B |
| 1966 | 115 hp | B18B |
| 1967 | 115 hp | B18B |
| 1968 | 115 hp | B18B |
1 factory vehicle, 1961–1968. Each year opens that model's engine table.