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Oldsmobile LX6/LX8 specs: 151 ci (2.5L) 4-cylinder, 4.00 x 3.00 in (101.6 x 76.2 mm) bore and stroke, 8.3:1 compression. Rated 85 hp, 1978–1980.
The Oldsmobile LX6/LX8 is oversquare — the 4" bore exceeds the 3" stroke by 33.3% — a layout that favors airflow and RPM over leverage at the crank. The 3" stroke does not reach 4,000 ft/min of mean piston speed until about 8,000 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 37.8 ci (619 cc).
8.3:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 5 engines in the Oldsmobile 151ci family, all of them 151 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated at 85 hp across 1978–1980.
| Displacement | 151 ci / 2.5 L |
|---|---|
| Bore | 4" |
| Stroke | 3" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 8.3:1 |
| Bore/stroke ratio | 1.333 |
| Fuel type | gas |
|---|---|
| Advertised HP | 85 hp |
| Years | 1978–1980 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1978 | LX6/LS6 net | 85 @ 4400 | 123 lb-ft @ 2800 | 8.3:1 |
Factory specification sheet.
| Bore/stroke character | 1.333 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,000 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.8 ci |
| Static compression | 8.3:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 1978 | 85 hp | LX6/LX8 |
| 1979 | 85 hp | LX6/LX8 |
| 1980 | 85 hp | LX6/LX8 |
5 factory vehicles, 1977–1980. Each year opens that model's engine table.