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Oldsmobile 350ci (1968–1975) specs: 350 ci (5.7L) 8-cylinder, 4.057 x 3.385 in (103 x 86 mm) bore and stroke. Rated 170-310 hp, 1968–1975.
The Oldsmobile 350ci (1968–1975) is oversquare — the 4.057" bore exceeds the 3.385" stroke by 19.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.385" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.773 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 43.8 ci (717 cc).
It is one of 11 engines in the Oldsmobile 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 9 factory variants share these dimensions, rated from 170 to 310 hp across 1968–1975.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4.057" |
| Stroke | 3.385" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9–10.25:1 (published figures vary) |
| Rod length | 6.002" |
| Rod ratio | 1.773 |
| Bore/stroke ratio | 1.199 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 170–310 hp |
| Years | 1968–1975 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1968 | L65 gross | 250 @ 4400 | 355 lb-ft @ 2600 | 9:1 |
| 1968 | L74 gross | 310 @ 4800 | 390 lb-ft @ 3200 | 10.25:1 |
| 1969 | gross | 250 @ 4400 | 355 lb-ft @ 2600 | 9:1 |
| 1970 | L65 gross | 250 @ 4400 | 355 lb-ft @ 2600 | 9:1 |
Factory specification sheet.
| Bore/stroke character | 1.199 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,385 ft/min — conservative for a street engine |
| Rod ratio | 1.773 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 43.8 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 |
|---|---|---|
| 1968 | 250 hp | — |
| 1968 | 310 hp | — |
| 1969 | 250 hp | — |
| 1970 | 250 hp | — |
| 1971 | — | — |
| 1972 | — | — |
| 1973 | — | — |
| 1974 | — | — |
| 1975 | 170 hp | — |
1 factory vehicle, 1968–1975. Each year opens that model's engine table.