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Oldsmobile Rocket (1965–1967) specs: 425 ci (7.0L) 8-cylinder, 4.125 x 3.975 in (104.8 x 101 mm) bore and stroke. Rated 300-385 hp, 1965–1967.
The Oldsmobile Rocket (1965–1967) is close to square: 4.1252" bore against 3.975" stroke, within 3.8%, which splits the difference between a high-revving layout and a torque layout. The 3.975" stroke puts mean piston speed at 4,000 ft/min around 6,050 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 53.1 ci (871 cc).
It is one of 14 engines in the Rocket family, sitting between the 260 ci and 455 ci members. 13 factory variants share these dimensions, rated from 300 to 385 hp across 1965–1967.
| Displacement | 425 ci / 7 L |
|---|---|
| Bore | 4.1252" |
| Stroke | 3.975" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9–10.5:1 (published figures vary) |
| Bore/stroke ratio | 1.038 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 300–385 hp |
| Years | 1965–1967 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1965 | gross | 300 @ 4400 | 430 lb-ft @ 2400 | 9:1 |
| 1965 | gross | 310 @ 4400 | 450 lb-ft @ 2400 | 10.25:1 |
| 1965 | gross | 360 @ 4800 | 470 lb-ft @ 2800 | 10.25:1 |
| 1965 | gross | 370 @ 4800 | 470 lb-ft @ 3200 | 10.5:1 |
| 1966 | gross | 310 @ 4400 | 450 lb-ft @ 2400 | 10.25:1 |
| 1966 | gross | 365 @ 4800 | 470 lb-ft @ 3200 | 10.25:1 |
| 1966 | gross | 375 @ 4800 | 470 lb-ft @ 3200 | 10.5:1 |
| 1966 | gross | 385 @ 4800 | 475 lb-ft @ 3200 | 10.5:1 |
| 1967 | gross | 300 @ 4400 | 430 lb-ft @ 2400 | 9:1 |
| 1967 | gross | 310 @ 4400 | 450 lb-ft @ 2400 | 10.25:1 |
| 1967 | L74 gross | 365 @ 4800 | 470 lb-ft @ 3200 | 10.25:1 |
| 1967 | L75 gross | 375 @ 4800 | 470 lb-ft @ 3200 | 10.5:1 |
| 1967 | gross | 385 @ 4800 | 480 lb-ft @ 3200 | 10.5:1 |
Factory specification sheet.
| Bore/stroke character | 1.038 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,975 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 53.1 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1965 | 300 hp | — |
| 1965 | 310 hp | — |
| 1965 | 360 hp | — |
| 1965 | 370 hp | — |
| 1966 | 310 hp | — |
| 1966 | 365 hp | — |
| 1966 | 375 hp | — |
| 1966 | 385 hp | — |
| 1967 | 300 hp | — |
| 1967 | 310 hp | — |
| 1967 | 365 hp | — |
| 1967 | 375 hp | — |
| 1967 | 385 hp | — |
4 factory vehicles, 1965–1967. Each year opens that model's engine table.