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Mercury 383ci (1958–1960) specs: 383 ci 8-cylinder, 4.30 x 3.30 in (109.2 x 83.8 mm) bore and stroke, 10.5:1 compression. Rated 280-330 hp, 1958–1960.
The Mercury 383ci (1958–1960) is oversquare — the 4.3" bore exceeds the 3.3" stroke by 30.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.3" stroke does not reach 4,000 ft/min of mean piston speed until about 7,250 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 47.9 ci (785 cc).
10.5:1 is in the range that usually runs on pump premium.
5 factory variants share these dimensions, rated from 280 to 330 hp across 1958–1960.
| Displacement | 383 ci |
|---|---|
| Bore | 4.3" |
| Stroke | 3.3" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 1.303 |
| Fuel type | gas |
|---|---|
| Advertised HP | 280–330 hp |
| Years | 1958–1960 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1958 | gross | 312 | 405 lb-ft | 10.5:1 |
| 1958 | gross | 330 | 425 lb-ft | 10.5:1 |
Factory specification sheet.
| Bore/stroke character | 1.303 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,300 ft/min — conservative for a street engine |
| Displacement per cylinder | 47.9 ci |
| Static compression | 10.5:1 — 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 |
|---|---|---|
| 1958 | 312 hp | — |
| 1958 | 330 hp | — |
| 1959 | 280 hp | — |
| 1959 | 322 hp | — |
| 1960 | 280 hp | — |
2 factory vehicles, 1958–1960. Each year opens that model's engine table.