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Oldsmobile 303 specs: 303 ci (5.0L) 8-cylinder, 3.75 x 3.437 in (95.3 x 87.3 mm) bore and stroke, 7.5:1 compression. Rated 135 hp. Rod ratio and piston speed.
The Oldsmobile Rocket V8 (303) is oversquare — the 3.75" bore exceeds the 3.437" stroke by 9.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.437" stroke puts mean piston speed at 4,000 ft/min around 7,000 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 37.9 ci (621 cc).
7.5:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 4 engines in the Rocket V8 family, the smallest at 303 ci. Factory fitments include the 88, 98, Super 88 and 2 others.
| Displacement | 303 ci / 5 L |
|---|---|
| Bore | 3.75" |
| Stroke | 3.437" |
| Cylinders | 8 |
| Compression ratio | 7.5:1 |
| Bore/stroke ratio | 1.091 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 135 hp |
| Bore/stroke character | 1.091 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,437 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.9 ci |
| Static compression | 7.5:1 — low by modern standards, generally happy on regular pump fuel |
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