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GMC LK5 specs: 169 ci (2.8L) 4-cylinder, 3.661 x 4.016 in (93 x 102 mm) bore and stroke. Rated 175 hp, 2004–2006. Used in the Chevrolet Colorado. DOHC.
The GMC Vortec 2800 (2.8L I4) (LK5) is undersquare — the 4.0157" stroke exceeds the 3.6614" bore by 8.8% — a layout that trades peak RPM for leverage and torque low in the range. The 4.0157" 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 4 cylinders displaces 42.3 ci (692 cc).
It is one of 2 engines in the Vortec 2800 (2.8L I4) family, all of them 169 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated at 175 hp across 2004–2006.
| Displacement | 169 ci / 2.8 L |
|---|---|
| Bore | 3.6614" |
| Stroke | 4.0157" |
| Cylinders | 4 |
| Configuration | I4 |
| Bore/stroke ratio | 0.912 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 175 hp |
| Years | 2004–2006 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2004 | LK5 net | 175 @ 5600 | 185 lb-ft @ 2800 | — |
| 2005 | LK5 net | 175 @ 5600 | 185 lb-ft @ 2800 | — |
| 2006 | LK5 net | 175 @ 5600 | 185 lb-ft @ 2800 | — |
Factory specification sheet.
| Bore/stroke character | 0.912 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,016 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 42.3 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 |
|---|---|---|
| 2004 | 175 hp | LK5 |
| 2005 | 175 hp | LK5 |
| 2006 | 175 hp | LK5 |
2 factory vehicles, 2004–2006. Each year opens that model's engine table.