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Mercedes-Benz M116.965 specs: 4.2L (256 ci) 8-cylinder, 92 x 78.9 mm (3.6220 x 3.1063 in) bore and stroke. Built 1986–1991. Used in the Mercedes-Benz S-Class.
The Mercedes-Benz M116.965 is oversquare — the 3.622" bore exceeds the 3.1063" stroke by 16.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.1063" stroke does not reach 4,000 ft/min of mean piston speed until about 7,750 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 32.0 ci (524 cc).
It is one of 3 engines in the Mercedes-Benz 256ci family, all of them 256 ci — the differences between them are in compression, heads and rating, not displacement. 6 factory variants share these dimensions across 1986–1991.
| Displacement | 256 ci / 4.2 L |
|---|---|
| Bore | 3.622" |
| Stroke | 3.1063" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9–10:1 (published figures vary) |
| Bore/stroke ratio | 1.166 |
| Fuel type | gas |
|---|---|
| Years | 1986–1991 |
| Bore/stroke character | 1.166 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,106 ft/min — conservative for a street engine |
| Displacement per cylinder | 32.0 ci |
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 |
|---|---|---|
| 1986 | — | M116.965 |
| 1987 | — | M116.965 |
| 1988 | — | M116.965 |
| 1989 | — | M116.965 |
| 1990 | — | M116.965 |
| 1991 | — | M116.965 |
1 factory vehicle, 1986–1991. Each year opens that model's engine table.