See other engines in this family
Buick 425ci specs: 425 ci (7.0L) 8-cylinder, 4.313 x 3.64 in (109.6 x 92.5 mm) bore and stroke, 10.25:1 compression. Rated 340-360 hp, 1963–1966.
The Buick 425ci is oversquare — the 4.313" bore exceeds the 3.64" stroke by 18.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.64" stroke puts mean piston speed at 4,000 ft/min around 6,600 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.709 is in the range most production engines fall in. Each of the 8 cylinders displaces 53.1 ci (871 cc).
10.25:1 is in the range that usually runs on pump premium.
6 factory variants share these dimensions, rated from 340 to 360 hp across 1963–1966.
| Displacement | 425 ci / 7 L |
|---|---|
| Bore | 4.313" |
| Stroke | 3.64" |
| Cylinders | 8 |
| Compression ratio | 10.25:1 |
| Rod length | 6.22" |
| Rod ratio | 1.709 |
| Bore/stroke ratio | 1.185 |
| Piston deck clearance | 0.028" |
| Induction | 1-4 |
|---|---|
| Advertised HP | 340–360 hp |
| Years | 1963–1966 |
| Bore/stroke character | 1.185 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,640 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.709 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 53.1 ci |
| Static compression | 10.25:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.875" |
|---|---|
| Exhaust valve diameter | 1.5" |
| Chamber volume | 123.72 cc |
| Rocker ratio | 1.6:1 |
| Lifter type | hydraulic |
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 |
|---|---|---|
| 1963 | 340 hp | — |
| 1964 | 340 hp | — |
| 1964 | 360 hp | — |
| 1965 | 340 hp | — |
| 1965 | 360 hp | — |
| 1966 | 340 hp | — |