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GMC 350 specs: 350 ci (5.7L) 8-cylinder, 4.00 x 3.50 in (101.6 x 88.9 mm) bore and stroke, 9:1 compression. Rated 310 hp. OHV. Rod ratio and piston speed.
The GMC Oldsmobile V8 (350) is oversquare — the 4" bore exceeds the 3.5" stroke by 14.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.5" stroke puts mean piston speed at 4,000 ft/min around 6,850 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.8 ci (717 cc).
9:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 7 engines in the Oldsmobile V8 family, sitting between the 307 ci and 425 ci members. Factory fitments include the Oldsmobile Cutlass, Oldsmobile 442, Oldsmobile Delta 88 and 1 other.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4" |
| Stroke | 3.5" |
| Cylinders | 8 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.143 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 310 hp |
| Bore/stroke character | 1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,500 ft/min — conservative for a street engine |
| Displacement per cylinder | 43.8 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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