See other engines in this family
American Motors 327ci (1957–1965) specs: 327 ci (5.4L) 8-cylinder, 4.00 x 3.25 in (101.6 x 82.6 mm) bore and stroke. Rated 250-270 hp, 1957–1965.
The American Motors 327ci (1957–1965) is oversquare — the 4" bore exceeds the 3.25" stroke by 23.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.25" stroke does not reach 4,000 ft/min of mean piston speed until about 7,400 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.962 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 40.9 ci (670 cc).
It is one of 3 engines in the American Motors 327ci family, all of them 327 ci — the differences between them are in compression, heads and rating, not displacement. 4 factory variants share these dimensions, rated from 250 to 270 hp across 1957–1965.
| Displacement | 327 ci / 5.4 L |
|---|---|
| Bore | 4" |
| Stroke | 3.25" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.7–9.7:1 (published figures vary) |
| Rod length | 6.375" |
| Rod ratio | 1.962 |
| Bore/stroke ratio | 1.231 |
| Fuel type | gas |
|---|---|
| Advertised HP | 250–270 hp |
| Years | 1957–1965 |
| Bore/stroke character | 1.231 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,250 ft/min — conservative for a street engine |
| Rod ratio | 1.962 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 40.9 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 |
|---|---|---|
| 1957 | 255 hp | — |
| 1958 | 270 hp | — |
| 1959 | 270 hp | — |
| 1965 | 250 hp | — |
2 factory vehicles, 1957–1965. Each year opens that model's engine table.