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GMC 330 specs: 330 ci (5.4L) 8-cylinder, 3.938 x 3.385 in (100 x 86 mm) bore and stroke, 10.25:1 compression. Rated 260 hp. OHV. Rod ratio and piston speed.
The GMC Oldsmobile V8 (330) is oversquare — the 3.938" bore exceeds the 3.385" stroke by 16.3% — 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. Each of the 8 cylinders displaces 41.3 ci (676 cc).
10.25:1 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 7 engines in the Oldsmobile V8 family, sitting between the 307 ci and 425 ci members. Factory fitments include the Oldsmobile F-85, Oldsmobile Cutlass, Oldsmobile 88.
| Displacement | 330 ci / 5.4 L |
|---|---|
| Bore | 3.938" |
| Stroke | 3.385" |
| Cylinders | 8 |
| Compression ratio | 10.25:1 |
| Bore/stroke ratio | 1.163 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 260 hp |
| Bore/stroke character | 1.163 — 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 |
| Displacement per cylinder | 41.3 ci |
| Static compression | 10.25:1 — in the range that usually runs on pump premium |
| Chamber volume | 60.19 cc |
|---|---|
| Rocker ratio | 1.6:1 |
| Lifter type | hydraulic |
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