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American Motors 304ci specs: 304 ci (5.0L) 8-cylinder, 3.75 x 3.44 in (95.3 x 87.4 mm) bore and stroke, 9:1 compression. Rated 210 hp, 1970.
The American Motors 304ci 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).
9:1 is low by modern standards and generally happy on regular pump fuel.
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.
| Displacement | 304 ci / 5 L |
|---|---|
| Bore | 3.75" |
| Stroke | 3.44" |
| Cylinders | 8 |
| Compression ratio | 9:1 |
| Rod length | 5.875" |
| Rod ratio | 1.708 |
| Bore/stroke ratio | 1.09 |
| Induction | 1-2 |
|---|---|
| Advertised HP | 210 hp |
| Years | 1970 |
| 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 |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
| Chamber volume | 50.7 cc |
|---|---|
| Rocker ratio | 1.6:1 |
| Lifter type | hydraulic |
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