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Oldsmobile 394 specs: 394 ci (6.5L) 8-cylinder, 4.126 x 3.685 in (104.8 x 93.6 mm) bore and stroke, 10.25:1 compression. Rated 315 hp. OHV.
The Oldsmobile Rocket V8 (394) is oversquare — the 4.126" bore exceeds the 3.685" stroke by 12.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.685" 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. Each of the 8 cylinders displaces 49.3 ci (807 cc).
10.25:1 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 4 engines in the Rocket V8 family, the largest at 394 ci. Factory fitments include the 98, Starfire, Dynamic 88 and 4 others.
| Displacement | 394 ci / 6.5 L |
|---|---|
| Bore | 4.126" |
| Stroke | 3.685" |
| Cylinders | 8 |
| Compression ratio | 10.25:1 |
| Bore/stroke ratio | 1.12 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 315 hp |
| Bore/stroke character | 1.120 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,685 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 49.3 ci |
| Static compression | 10.25:1 — in the range that usually runs on pump premium |
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