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Mercedes-Benz M117 specs: 5.0L (303 ci) 8-cylinder, 96.5 x 85 mm (3.7992 x 3.3465 in) bore and stroke, 9.2:1 compression. Built 1984–1985.
The Mercedes-Benz M117 is oversquare — the 3.7992" bore exceeds the 3.3465" stroke by 13.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.3465" stroke does not reach 4,000 ft/min of mean piston speed until about 7,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 37.9 ci (621 cc).
9.2:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 2 engines in the Mercedes-Benz 303ci family, all of them 303 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions across 1984–1985.
| Displacement | 303 ci / 5 L |
|---|---|
| Bore | 3.7992" |
| Stroke | 3.3465" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9.2:1 * |
| Bore/stroke ratio | 1.135 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Years | 1984–1985 |
| Bore/stroke character | 1.135 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,347 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.9 ci |
| Static compression | 9.2:1 — 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 |
|---|---|---|
| 1984 | — | M117 |
| 1985 | — | M117 |
1 factory vehicle, 1984–1985. Each year opens that model's engine table.