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GMC 502 specs: 502 ci (8.2L) 8-cylinder, 4.466 x 4.00 in (113.4 x 101.6 mm) bore and stroke, 9.6:1 compression. Rated 338 hp. OHV. Rod ratio and piston speed.
The GMC Big Block Chevy (502) is oversquare — the 4.466" bore exceeds the 4" stroke by 11.7% — a layout that favors airflow and RPM over leverage at the crank. The 4" stroke puts mean piston speed at 4,000 ft/min around 6,000 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 62.8 ci (1,028 cc).
9.6:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 5 engines in the Big Block Chevy family, the largest at 502 ci. Factory fitments include the GMC Performance Crate Engines.
| Displacement | 502 ci / 8.2 L |
|---|---|
| Bore | 4.466" |
| Stroke | 4" |
| Cylinders | 8 |
| Compression ratio | 9.6:1 |
| Bore/stroke ratio | 1.117 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 338 hp |
| Bore/stroke character | 1.117 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 4,000 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 62.8 ci |
| Static compression | 9.6:1 — in the range that usually runs on pump premium |
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