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BMW M30B30 specs: 3.0L (182 ci) 6-cylinder, 89 x 80 mm (3.5039 x 3.1496 in) bore and stroke, 8.1:1 compression. Rated 176 hp, 1975–1978.
The BMW M30B30 is oversquare — the 3.5039" bore exceeds the 3.1496" stroke by 11.2% — 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 6 cylinders displaces 30.3 ci (497 cc).
8.1:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 7 engines in the BMW 182ci family, all of them 182 ci — the differences between them are in compression, heads and rating, not displacement. 4 factory variants share these dimensions, rated at 176 hp across 1975–1978.
| Displacement | 182 ci / 3 L |
|---|---|
| Bore | 3.5039" |
| Stroke | 3.1496" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 8.1:1 * |
| Bore/stroke ratio | 1.112 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Advertised HP | 176 hp |
| Years | 1975–1978 |
| Bore/stroke character | 1.112 — 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 | 8.1:1 — 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 |
|---|---|---|
| 1975 | 176 hp | M30B30 |
| 1976 | 176 hp | M30B30 |
| 1977 | 176 hp | M30B30 |
| 1978 | 176 hp | M30B30 |
2 factory vehicles, 1975–1978. Each year opens that model's engine table.