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Pontiac 370ci specs: 370 ci (6.1L) 8-cylinder, 4.063 x 3.563 in (103.2 x 90.5 mm) bore and stroke, 8.6:1 compression. Rated 240 hp, 1958.
The Pontiac 370ci is oversquare — the 4.063" bore exceeds the 3.563" stroke by 14.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.563" 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. A rod ratio of 1.859 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 46.3 ci (758 cc).
8.6:1 is low by modern standards and generally happy on regular pump fuel.
| Displacement | 370 ci / 6.1 L |
|---|---|
| Bore | 4.063" |
| Stroke | 3.563" |
| Cylinders | 8 |
| Compression ratio | 8.6:1 |
| Rod length | 6.625" |
| Rod ratio | 1.859 |
| Bore/stroke ratio | 1.14 |
| Piston deck clearance | 0" |
| Induction | 1-2 |
|---|---|
| Advertised HP | 240 hp |
| Years | 1958 |
| Bore/stroke character | 1.140 — 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 |
| Rod ratio | 1.859 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 46.3 ci |
| Static compression | 8.6:1 — low by modern standards, generally happy on regular pump fuel |
| Intake valve diameter | 1.88" |
|---|---|
| Exhaust valve diameter | 1.6" |
| Chamber volume | 70.2 cc |
| Rocker ratio | 1.5:1 |
| Lifter type | hydraulic |
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