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Oldsmobile 394 specs: 394 ci (6.5L) 8-cylinder, 4.06 x 3.80 in (103.1 x 96.5 mm) bore and stroke, 9.75:1 compression. Rated 315 hp. OHV.
The Oldsmobile Rocket (394) is oversquare — the 4.0598" bore exceeds the 3.8" stroke by 6.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.8" stroke puts mean piston speed at 4,000 ft/min around 6,300 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 49.3 ci (807 cc).
9.75:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 15 engines in the Rocket family, sitting between the 260 ci and 455 ci members. Factory fitments include the Oldsmobile 98, Oldsmobile Starfire, Oldsmobile Dynamic 88 and 1 other.
| Displacement | 394 ci / 6.5 L |
|---|---|
| Bore | 4.0598" |
| Stroke | 3.8" |
| Cylinders | 8 |
| Compression ratio | 9.75:1 |
| Bore/stroke ratio | 1.068 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 315 hp |
| Bore/stroke character | 1.068 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,800 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 49.3 ci |
| Static compression | 9.75:1 — in the range that usually runs on pump premium |
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