See other engines in this family
Pontiac LD8 specs: 279 ci (4.6L) 8-cylinder, 3.661 x 3.307 in (93 x 84 mm) bore and stroke, 10:1 compression. Rated 275 hp, 2004–2005.
The Pontiac 279ci (LD8) is oversquare — the 3.6614" bore exceeds the 3.3071" stroke by 10.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.3071" stroke does not reach 4,000 ft/min of mean piston speed until about 7,250 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 34.9 ci (571 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.
2 factory variants share these dimensions, rated at 275 hp across 2004–2005.
| Displacement | 279 ci / 4.6 L |
|---|---|
| Bore | 3.6614" |
| Stroke | 3.3071" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 10:1 * |
| Bore/stroke ratio | 1.107 |
* Compression ratio from a single source; not yet cross-verified.
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 275 hp |
| Years | 2004–2005 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2004 | LD8 net | 275 @ 5600 | 300 lb-ft @ 4000 | — |
| 2005 | LD8 net | 275 @ 5600 | 300 lb-ft @ 4000 | — |
Factory specification sheet.
| Bore/stroke character | 1.107 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,307 ft/min — conservative for a street engine |
| Displacement per cylinder | 34.9 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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 | 275 hp | LD8 |
| 2005 | 275 hp | LD8 |
4 factory vehicles, 1994–2005. Each year opens that model's engine table.