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Pontiac 347ci (1957) specs: 347 ci 8-cylinder, 3.938 x 3.563 in (100 x 90.5 mm) bore and stroke. Built 1957. Used in the Pontiac Bonneville.
The Pontiac 347ci (1957) is oversquare — the 3.9375" bore exceeds the 3.5625" stroke by 10.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.5625" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.4 ci (711 cc).
| Displacement | 347 ci |
|---|---|
| Bore | 3.9375" |
| Stroke | 3.5625" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.5–10:1 (published figures vary) |
| Bore/stroke ratio | 1.105 |
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Years | 1957 |
| Bore/stroke character | 1.105 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,563 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 43.4 ci |
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1 factory vehicle, 1957. Each year opens that model's engine table.