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American Motors 304ci (1971–1978) specs: 304 ci (5.0L) 8-cylinder, 3.75 x 3.44 in (95.3 x 87.4 mm) bore and stroke. Rated 121-210 hp, 1971–1978.
The American Motors 304ci (1971–1978) is oversquare — the 3.75" bore exceeds the 3.44" stroke by 9.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.44" stroke puts mean piston speed at 4,000 ft/min around 7,000 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.708 is in the range most production engines fall in. Each of the 8 cylinders displaces 38.0 ci (623 cc).
It is one of 3 engines in the American Motors 304ci family, all of them 304 ci — the differences between them are in compression, heads and rating, not displacement. 6 factory variants share these dimensions, rated from 121 to 210 hp across 1971–1978.
| Displacement | 304 ci / 5 L |
|---|---|
| Bore | 3.75" |
| Stroke | 3.44" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 5.875" |
| Rod ratio | 1.708 |
| Bore/stroke ratio | 1.09 |
| Fuel type | gas |
|---|---|
| Advertised HP | 121–210 hp |
| Years | 1971–1978 |
| Bore/stroke character | 1.090 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,440 ft/min — conservative for a street engine |
| Rod ratio | 1.708 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 38.0 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 | 210 hp | — |
| 1972 | 150 hp | — |
| 1973 | 150 hp | — |
| 1974 | 150 hp | — |
| 1977 | 121 hp | — |
| 1978 | 130 hp | — |