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GMC LM4 specs: 325 ci (5.3L) 8-cylinder, 3.78 x 3.622 in (96 x 92 mm) bore and stroke. Rated 290 hp, 2003–2004. Used in the GMC Envoy and Chevrolet SSR. OHV.
The GMC 325ci (LM4) 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).
It is one of 15 engines in the GMC 325ci family, all of them 325 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated at 290 hp across 2003–2004.
| Displacement | 325 ci / 5.3 L |
|---|---|
| Bore | 3.7799" |
| Stroke | 3.622" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.044 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 290 hp |
| Years | 2003–2004 |
| 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 |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2003 | 290 hp | LM4 |
| 2004 | 290 hp | LM4 |
4 factory vehicles, 2003–2004. Each year opens that model's engine table.