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GMC L25 specs: 292 ci (4.8L) 6-cylinder, 3.875 x 4.125 in (98.4 x 104.8 mm) bore and stroke. Rated 165-170 hp, 1967–1971. Used in the Chevrolet C/K Pickup.
The GMC Chevy Straight-6 (194/230/250/292) (L25) is undersquare — the 4.125" stroke exceeds the 3.875" bore by 6.1% — a layout that trades peak RPM for leverage and torque low in the range. The 4.125" stroke puts mean piston speed at 4,000 ft/min around 5,800 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 48.7 ci (798 cc).
It is one of 10 engines in the Chevy Straight-6 (194/230/250/292) family, the largest at 292 ci. 5 factory variants share these dimensions, rated from 165 to 170 hp across 1967–1971.
| Displacement | 292 ci / 4.8 L |
|---|---|
| Bore | 3.875" |
| Stroke | 4.125" |
| Cylinders | 6 |
| Configuration | I6 |
| Bore/stroke ratio | 0.939 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 165–170 hp |
| Years | 1967–1971 |
| Bore/stroke character | 0.939 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,125 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 48.7 ci |
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These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1967 | 170 hp | L25 |
| 1968 | 170 hp | L25 |
| 1969 | 170 hp | L25 |
| 1970 | 170 hp | L25 |
| 1971 | 165 hp | L25 |