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Oldsmobile 394ci (1959–1964) specs: 394 ci (6.5L) 8-cylinder, 4.124 x 3.688 in (104.7 x 93.7 mm) bore and stroke. Rated 250-345 hp, 1959–1964.
The Oldsmobile 394ci (1959–1964) is oversquare — the 4.124" bore exceeds the 3.688" stroke by 11.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.688" stroke puts mean piston speed at 4,000 ft/min around 6,500 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.898 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 49.3 ci (807 cc).
It is one of 2 engines in the Oldsmobile 394ci family, all of them 394 ci — the differences between them are in compression, heads and rating, not displacement. 16 factory variants share these dimensions, rated from 250 to 345 hp across 1959–1964.
| Displacement | 394 ci / 6.5 L |
|---|---|
| Bore | 4.124" |
| Stroke | 3.688" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.75–10.5:1 (published figures vary) |
| Rod length | 7" |
| Rod ratio | 1.898 |
| Bore/stroke ratio | 1.118 |
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 250–345 hp |
| Years | 1959–1964 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1959 | gross | 315 @ 4600 | 435 lb-ft @ 2800 | 9.75:1 | — | — | — |
| 1960 | gross | 315 @ 4600 | 435 lb-ft @ 2800 | 9.75:1 | — | — | — |
| 1961 | gross | 250 @ 4400 | 405 lb-ft @ 2400 | 8.75:1 | — | — | — |
| 1961 | gross | 325 @ 4600 | 435 lb-ft @ 2800 | 10:1 | — | 0.427" / 0.435" | — |
| 1962 | gross | 260 | — | 8.75:1 | — | — | — |
| 1962 | gross | 280 @ 4400 | 430 lb-ft @ 2400 | 10.25:1 | — | — | — |
| 1962 | gross | 330 @ 4600 | 440 lb-ft @ 2800 | 10.25:1 | — | — | — |
| 1962 | gross | 345 @ 4600 | 440 lb-ft @ 3200 | 10.5:1 | — | — | — |
| 1963 | gross | 260 @ 4400 | 410 lb-ft @ 4400 | 8.75:1 | — | — | — |
| 1963 | gross | 280 @ 4400 | 430 lb-ft @ 2400 | 10.25:1 | 244° / 250° | 0.428" / 0.435" | 108.5° |
| 1963 | gross | 330 @ 4600 | 440 lb-ft @ 2800 | 10.25:1 | 250° / 264° | 0.435" | 110.5° |
| 1963 | gross | 345 @ 4800 | 440 lb-ft @ 3200 | 10.5:1 | 278° / 260° | 0.444" / 0.435" | 114° |
Factory specification sheet. Durations are the factory's advertised figures at the basis printed on the sheet, not duration at .050" lift; lobe separation is calculated from the printed valve timing.
| Bore/stroke character | 1.118 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,688 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.898 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 49.3 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 | 315 hp | — |
| 1960 | 315 hp | — |
| 1961 | 250 hp | — |
| 1961 | 325 hp | — |
| 1961 | 330 hp | — |
| 1962 | 260 hp | — |
| 1962 | 280 hp | — |
| 1962 | 330 hp | — |
| 1962 | 345 hp | — |
| 1963 | 260 hp | — |
| 1963 | 280 hp | — |
| 1963 | 330 hp | — |
| 1963 | 345 hp | — |
| 1964 | 260 hp | — |
| 1964 | 330 hp | — |
| 1964 | 345 hp | — |
3 factory vehicles, 1959–1964. Each year opens that model's engine table.