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Pontiac 389ci (1959–1964) specs: 389 ci (6.4L) 8-cylinder, 4.062 x 3.75 in (103.2 x 95.3 mm) bore and stroke. Rated 215-348 hp, 1959–1964.
The Pontiac 389ci (1959–1964) is oversquare — the 4.062" bore exceeds the 3.75" stroke by 8.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.75" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.767 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 48.6 ci (797 cc).
It is one of 5 engines in the Pontiac 389ci family, all of them 389 ci — the differences between them are in compression, heads and rating, not displacement. 16 factory variants share these dimensions, rated from 215 to 348 hp across 1959–1964.
| Displacement | 389 ci / 6.4 L |
|---|---|
| Bore | 4.062" |
| Stroke | 3.75" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.6–10.75:1 (published figures vary) |
| Rod length | 6.625" |
| Rod ratio | 1.767 |
| Bore/stroke ratio | 1.083 |
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 215–348 hp |
| Years | 1959–1964 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1959 | gross | 245 @ 4200 | 392 lb-ft @ 2000 | 8.6:1 |
| 1959 | gross | 260 @ 4200 | 400 lb-ft @ 2800 | 8.6:1 |
| 1959 | gross | 280 @ 4400 | 408 lb-ft @ 2800 | 10:1 |
| 1959 | gross | 300 @ 4600 | 420 lb-ft @ 2800 | 10:1 |
| 1959 | gross | 315 @ 4600 | 425 lb-ft @ 3200 | 10.5:1 |
| 1960 | gross | 281 @ 4400 | 407 lb-ft @ 2800 | 8.6:1 |
| 1960 | gross | 283 @ 4400 | 413 lb-ft @ 2800 | 10.25:1 |
| 1960 | gross | 303 @ 4600 | 425 lb-ft @ 2800 | 10.25:1 |
| 1960 | gross | 318 @ 4600 | 430 lb-ft @ 3200 | 10.75:1 |
Factory specification sheet.
| Bore/stroke character | 1.083 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,750 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.767 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 48.6 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 |
|---|---|---|
| 1959 | 245 hp | — |
| 1959 | 260 hp | — |
| 1959 | 280 hp | — |
| 1959 | 300 hp | — |
| 1959 | 315 hp | — |
| 1959 | 330 hp | — |
| 1959 | 345 hp | — |
| 1960 | — | — |
| 1960 | 235 hp | — |
| 1960 | 281 hp | — |
| 1960 | 283 hp | — |
| 1960 | 303 hp | — |
| 1960 | 318 hp | — |
| 1960 | 333 hp | — |
| 1960 | 348 hp | — |
| 1964 | 215 hp | — |
2 factory vehicles, 1959–1964. Each year opens that model's engine table.