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Buick 401ci (1959–1962) specs: 401 ci (6.6L) 8-cylinder, 4.188 x 3.64 in (106.4 x 92.5 mm) bore and stroke. Rated 265-325 hp, 1959–1962.
The Buick 401ci (1959–1962) is oversquare — the 4.188" bore exceeds the 3.64" stroke by 15.1% — 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 50.1 ci (821 cc).
It is one of 3 engines in the Buick 401ci family, all of them 401 ci — the differences between them are in compression, heads and rating, not displacement. 6 factory variants share these dimensions, rated from 265 to 325 hp across 1959–1962.
| Displacement | 401 ci / 6.6 L |
|---|---|
| Bore | 4.188" |
| Stroke | 3.64" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9–10.5:1 (published figures vary) |
| Rod length | 6.22" |
| Rod ratio | 1.709 |
| Bore/stroke ratio | 1.151 |
| Fuel type | gas |
|---|---|
| Firing order | 1-2-7-8-4-5-6-3 |
| Advertised HP | 265–325 hp |
| Years | 1959–1962 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1959 | gross | 325 @ 4400 | 445 lb-ft @ 2800 | 10.5:1 | 290° / 299° | 0.439" | 108.75° |
| 1960 | gross | 325 @ 4400 * | 445 lb-ft * | 10.25:1 * | — | — | — |
| 1961 | gross | 325 @ 4400 | 445 lb-ft @ 2800 | 10.25:1 | — | — | — |
| 1962 | gross | 265 @ 4400 | 412 lb-ft @ 2400 | 9:1 | — | — | — |
| 1962 | gross | 280 @ 4400 | 424 lb-ft @ 2400 | 10.25:1 | — | — | — |
| 1962 | gross | 325 @ 4400 | 445 lb-ft @ 2800 | 10.25:1 | — | — | — |
Factory specification sheet. Durations are the factory's advertised figures at the basis printed on the sheet, not duration at .050" lift; lobe separation is calculated from the printed valve timing. * Not yet cross-verified.
| Bore/stroke character | 1.151 — 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 | 50.1 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 |
|---|---|---|
| 1959 | 325 hp | — |
| 1960 | 325 hp | — |
| 1961 | 325 hp | — |
| 1962 | 265 hp | — |
| 1962 | 280 hp | — |
| 1962 | 325 hp | — |
2 factory vehicles, 1959–1962. Each year opens that model's engine table.