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Oldsmobile 350ci specs: 350 ci (5.7L) 8-cylinder, 4.057 x 3.385 in (103 x 86 mm) bore and stroke, 9.591:1 compression. Rated 140-155 hp, 1976. OHV.
The Oldsmobile 350ci 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).
9.591:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 8 engines in the Oldsmobile 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated from 140 to 155 hp in 1976.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4.057" |
| Stroke | 3.385" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9.591:1 |
| 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 |
| Advertised HP | 140–155 hp |
| Years | 1976 |
| 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 |
| Static compression | 9.591:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.88" |
|---|---|
| Exhaust valve diameter | 1.555" |
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 |
|---|---|---|
| 1976 | 140 hp | — |
| 1976 | 155 hp | — |