See other engines in this family
Mercedes-Benz M116 3.8 (3839 cc) specs: 3.8L (234 ci) 8-cylinder, 88 x 78.9 mm (3.4646 x 3.1063 in) bore and stroke, 8.3:1 compression. Built 1981–1985.
The Mercedes-Benz M116 3.8 (3839 cc) is oversquare — the 3.4646" bore exceeds the 3.1063" stroke by 11.5% — 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 29.3 ci (479 cc).
8.3:1 is low by modern standards and generally happy on regular pump fuel.
5 factory variants share these dimensions across 1981–1985.
| Displacement | 234 ci / 3.8 L |
|---|---|
| Bore | 3.4646" * |
| Stroke | 3.1063" * |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.3:1 * |
| Bore/stroke ratio | 1.115 |
* Bore, stroke and compression ratio from a single source; not yet cross-verified.
How to tell which you have: Every US-market 380 SE, SEL, SEC and SL of 1981-85 has the 3,839 cc M116 (88 x 78.9 mm); the 3,818 cc version was never sold in the US.
| Fuel type | gas |
|---|---|
| Years | 1981–1985 |
| Bore/stroke character | 1.115 — 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 | 29.3 ci |
| Static compression | 8.3:1 — 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 |
|---|---|---|
| 1981 | — | M116 3.8 (3839 cc) |
| 1982 | — | M116 3.8 (3839 cc) |
| 1983 | — | M116 3.8 (3839 cc) |
| 1984 | — | M116 3.8 (3839 cc) |
| 1985 | — | M116 3.8 (3839 cc) |
2 factory vehicles, 1981–1985. Each year opens that model's engine table.