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American Motors 401ci (1971–1974) specs: 401 ci (6.6L) 8-cylinder, 4.165 x 3.68 in (105.8 x 93.5 mm) bore and stroke. Rated 235-330 hp, 1971–1974.
The American Motors 401ci (1971–1974) is oversquare — the 4.165" bore exceeds the 3.68" stroke by 13.2% — a layout that favors airflow and RPM over leverage at the crank. The 3.68" stroke puts mean piston speed at 4,000 ft/min around 6,500 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 50.1 ci (821 cc).
4 factory variants share these dimensions, rated from 235 to 330 hp across 1971–1974.
| Displacement | 401 ci / 6.6 L |
|---|---|
| Bore | 4.165" |
| Stroke | 3.68" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.132 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 235–330 hp |
| Years | 1971–1974 |
| Bore/stroke character | 1.132 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,680 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 50.1 ci |
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These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1971 | 330 hp | — |
| 1972 | 255 hp | — |
| 1973 | 255 hp | — |
| 1974 | 235 hp | — |