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Oldsmobile 307 specs: 307 ci (5.0L) 8-cylinder, 3.80 x 3.35 in (96.5 x 85.1 mm) bore and stroke, 8:1 compression. Rated 140 hp. Rod ratio and piston speed.
The Oldsmobile Rocket (307) is oversquare — the 3.8" bore exceeds the 3.35" stroke by 13.4% — a layout that favors airflow and RPM over leverage at the crank. The 3.35" stroke does not reach 4,000 ft/min of mean piston speed until about 7,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 38.4 ci (629 cc).
8:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 15 engines in the Rocket family, sitting between the 260 ci and 455 ci members. Factory fitments include the Oldsmobile Cutlass, Oldsmobile Delta 88, Oldsmobile Custom Cruiser and 4 others.
| Displacement | 307 ci / 5 L |
|---|---|
| Bore | 3.8" |
| Stroke | 3.35" |
| Cylinders | 8 |
| Compression ratio | 8:1 |
| Bore/stroke ratio | 1.134 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 140 hp |
| Bore/stroke character | 1.134 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,350 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.4 ci |
| Static compression | 8:1 — low by modern standards, generally happy on regular pump fuel |
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