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Oldsmobile 215ci specs: 215 ci (3.5L) 8-cylinder, 3.50 x 2.80 in (88.9 x 71.1 mm) bore and stroke, 10.75:1 compression. Rated 195 hp, 1963.
The Oldsmobile 215ci is oversquare — the 3.5" bore exceeds the 2.8" stroke by 25.0% — a layout that favors airflow and RPM over leverage at the crank. The 2.8" stroke does not reach 4,000 ft/min of mean piston speed until about 8,550 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 2 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 26.9 ci (440 cc).
10.75:1 is in the range that usually runs on pump premium.
It is one of 4 engines in the Oldsmobile 215ci family, all of them 215 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 215 ci / 3.5 L |
|---|---|
| Bore | 3.5" |
| Stroke | 2.8" |
| Cylinders | 8 |
| Compression ratio | 10.75:1 |
| Rod length | 5.6" |
| Rod ratio | 2 |
| Bore/stroke ratio | 1.25 |
| Induction | 1-4 |
|---|---|
| Advertised HP | 195 hp |
| Years | 1963 |
| Bore/stroke character | 1.250 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,800 ft/min — conservative for a street engine |
| Rod ratio | 2 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 26.9 ci |
| Static compression | 10.75:1 — in the range that usually runs on pump premium |
| Chamber volume | 38.84 cc |
|---|---|
| Rocker ratio | 1.6:1 |
| Lifter type | hydraulic |
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