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Pontiac LN7 specs: 181 ci (3.0L) 6-cylinder, 3.80 x 2.66 in (96.5 x 67.6 mm) bore and stroke. Rated 125 hp, 1985–1987. Used in the Pontiac Grand Am.
The Pontiac 181ci (LN7) is oversquare — the 3.8" bore exceeds the 2.66" stroke by 42.9% — a layout that favors airflow and RPM over leverage at the crank. The 2.66" stroke does not reach 4,000 ft/min of mean piston speed until about 9,000 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 30.2 ci (494 cc).
3 factory variants share these dimensions, rated at 125 hp across 1985–1987.
| Displacement | 181 ci / 3 L |
|---|---|
| Bore | 3.8" |
| Stroke | 2.66" |
| Cylinders | 6 |
| Configuration | V6 |
| Compression ratio | 8.4–9:1 (published figures vary) |
| Bore/stroke ratio | 1.429 |
| Fuel type | gas |
|---|---|
| Advertised HP | 125 hp |
| Years | 1985–1987 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1985 | LN7 net | 125 @ 4900 | 150 lb-ft @ 2400 | 9:1 |
| 1986 | LN7 net | 125 @ 4900 | 150 lb-ft @ 2400 | 8.4:1 |
| 1987 | LN7 net | 125 @ 4900 | 150 lb-ft @ 2400 | 9:1 |
Factory specification sheet.
| Bore/stroke character | 1.429 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,660 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.2 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 |
|---|---|---|
| 1985 | 125 hp | LN7 |
| 1986 | 125 hp | LN7 |
| 1987 | 125 hp | LN7 |
6 factory vehicles, 1985–1988. Each year opens that model's engine table.