American Motors 390ci specs: 4.165 x 3.574 in (105.8 x 90.8 mm) bore and stroke, shared by all 4 versions. Displacement, compression and factory ratings.
| Displacement | 390 ci |
|---|---|
| Cylinders | 8 |
| Bore | 4.165" |
| Stroke | 3.574" |
| Compression | 10.0–10.2:1 |
| Advertised power | 315–340 hp |
| Years | 1968–1970 |
| Cylinder head data | 2 of 4 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| X | 390 ci | 4.165" × 3.574" | — | 315 |
| American Motors 390ci (1969) | 390 ci | 4.165" × 3.574" | — | 315 |
| American Motors 390ci · 4.165" × 3.574" · 10.2:1 | 390 ci | 4.165" × 3.574" | 10.2:1 | 315 |
| American Motors 390ci · 4.165" × 3.574" · 10:1 | 390 ci | 4.165" × 3.574" | 10:1 | 325–340 |
All are oversquare — bore larger than stroke, which favours revs over low-end torque.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.