See other engines in this family
Oldsmobile 394ci specs: 394 ci (6.5L) 8-cylinder, 4.124 x 3.688 in (104.7 x 93.7 mm) bore and stroke, 10.25:1 compression. Rated 280 hp, 1964.
The Oldsmobile 394ci is oversquare — the 4.124" bore exceeds the 3.688" stroke by 11.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.688" stroke puts mean piston speed at 4,000 ft/min around 6,500 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.898 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 49.3 ci (807 cc).
10.25:1 is in the range that usually runs on pump premium.
| Displacement | 394 ci / 6.5 L |
|---|---|
| Bore | 4.124" |
| Stroke | 3.688" |
| Cylinders | 8 |
| Compression ratio | 10.25:1 |
| Rod length | 7" |
| Rod ratio | 1.898 |
| Bore/stroke ratio | 1.118 |
| Induction | 1-4 |
|---|---|
| Advertised HP | 280 hp |
| Years | 1964 |
| Bore/stroke character | 1.118 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,688 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.898 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 49.3 ci |
| Static compression | 10.25:1 — in the range that usually runs on pump premium |
| Chamber volume | 70.9 cc |
|---|---|
| Rocker ratio | 1.8:1 |
| Lifter type | hydraulic |
Each link opens the calculator with this engine's specs already filled in.