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Oldsmobile 260 specs: 260 ci (4.3L) 8-cylinder, 3.70 x 3.06 in (94 x 77.7 mm) bore and stroke, 8:1 compression. Rated 110 hp. OHV. Rod ratio and piston speed.
The Oldsmobile Rocket (260) is oversquare — the 3.7" bore exceeds the 3.0598" stroke by 20.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.0598" stroke does not reach 4,000 ft/min of mean piston speed until about 7,850 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 32.5 ci (533 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, the smallest at 260 ci. Factory fitments include the Oldsmobile Cutlass, Oldsmobile Omega, Oldsmobile Starfire and 3 others.
| Displacement | 260 ci / 4.3 L |
|---|---|
| Bore | 3.7" |
| Stroke | 3.0598" |
| Cylinders | 8 |
| Compression ratio | 8:1 |
| Bore/stroke ratio | 1.209 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 110 hp |
| Bore/stroke character | 1.209 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,060 ft/min — conservative for a street engine |
| Displacement per cylinder | 32.5 ci |
| Static compression | 8:1 — low by modern standards, generally happy on regular pump fuel |
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