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GMC L850 specs: 134.2 ci (2.2L) 4-cylinder, 3.386 x 3.724 in (86 x 94.6 mm) bore and stroke, 10:1 compression. Rated 145 hp. DOHC. Rod ratio and piston speed.
The GMC L850 is undersquare — the 3.7244" stroke exceeds the 3.3858" bore by 9.1% — a layout that trades peak RPM for leverage and torque low in the range. The 3.7244" stroke puts mean piston speed at 4,000 ft/min around 6,450 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 33.6 ci (550 cc).
10:1 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 6 engines in the Ecotec I4 family, sitting between the 83.2 ci and 145 ci members. Factory fitments include the Chevrolet Cavalier, Chevrolet Cobalt, Pontiac G5 and 1 other.
| Displacement | 134.2 ci / 2.2 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.7244" |
| Cylinders | 4 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 0.909 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 145 hp |
| Bore/stroke character | 0.909 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,724 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 33.5 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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