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American Motors 327ci specs: 327 ci (5.4L) 8-cylinder, 4.00 x 3.25 in (101.6 x 82.6 mm) bore and stroke, 9.7:1 compression. Rated 270 hp, 1960–1966.
The American Motors 327ci 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).
9.7:1 is in the range that usually runs on pump premium.
It is one of 2 engines in the American Motors 327ci family, all of them 327 ci — the differences between them are in compression, heads and rating, not displacement. 7 factory variants share these dimensions, rated at 270 hp across 1960–1966.
| Displacement | 327 ci / 5.4 L |
|---|---|
| Bore | 4" |
| Stroke | 3.25" |
| Cylinders | 8 |
| Compression ratio | 9.7:1 |
| Rod length | 6.375" |
| Rod ratio | 1.962 |
| Bore/stroke ratio | 1.231 |
| Piston deck clearance | 0.042" |
| Induction | 1-4 |
|---|---|
| Advertised HP | 270 hp |
| Years | 1960–1966 |
| 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 |
| Static compression | 9.7:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.787" |
|---|---|
| Exhaust valve diameter | 1.406" |
| Chamber volume | 60.5 cc |
| Rocker ratio | 1.5:1 |
| Lifter type | hydraulic |
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 |
|---|---|---|
| 1960 | 270 hp | — |
| 1961 | 270 hp | — |
| 1962 | 270 hp | — |
| 1963 | 270 hp | — |
| 1964 | 270 hp | — |
| 1965 | 270 hp | — |
| 1966 | 270 hp | — |