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Chevrolet LS4 specs: 325 ci (5.3L) 8-cylinder, 3.78 x 3.622 in (96 x 92 mm) bore and stroke, 10:1 compression. Rated 303 hp. OHV. Rod ratio and piston speed.
The Chevrolet LS (LS4) is close to square: 3.7799" bore against 3.622" stroke, within 4.4%, which splits the difference between a high-revving layout and a torque layout. The 3.622" stroke puts mean piston speed at 4,000 ft/min around 6,650 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 40.6 ci (666 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 57 engines in the LS family, sitting between the 293 ci and 454 ci members. Factory fitments include the Chevrolet Impala SS, Chevrolet Monte Carlo SS, Pontiac Grand Prix GXP and 1 other.
| Displacement | 325 ci / 5.3 L |
|---|---|
| Bore | 3.7799" |
| Stroke | 3.622" |
| Cylinders | 8 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.044 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 303 hp |
| Bore/stroke character | 1.044 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,622 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 40.6 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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