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Oldsmobile 455 specs: 455 ci (7.5L) 8-cylinder, 4.125 x 4.30 in (104.8 x 109.2 mm) bore and stroke, 10.5:1 compression. Rated 370 hp. OHV.
The Oldsmobile Rocket (455) is close to square: 4.1252" bore against 4.3" stroke, within 4.1%, which splits the difference between a high-revving layout and a torque layout. The 4.3" stroke puts mean piston speed at 4,000 ft/min around 5,600 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 56.9 ci (932 cc).
10.5:1 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, the largest at 455 ci. Factory fitments include the Oldsmobile 442, Oldsmobile Toronado, Oldsmobile Cutlass and 3 others.
| Displacement | 455 ci / 7.5 L |
|---|---|
| Bore | 4.1252" |
| Stroke | 4.3" |
| Cylinders | 8 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 0.959 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 370 hp |
| Bore/stroke character | 0.959 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,300 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 56.9 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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