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Oldsmobile LF9 specs: 350 ci (5.7L) 8-cylinder, 4.00 x 3.50 in (101.6 x 88.9 mm) bore and stroke. Rated 105-125 hp, 1978–1985.
The Oldsmobile Diesel V8 (LF9) is oversquare — the 4" bore exceeds the 3.5" stroke by 14.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.5" stroke puts mean piston speed at 4,000 ft/min around 6,850 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.8 ci (717 cc).
It is one of 2 engines in the Diesel V8 family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 10 factory variants share these dimensions, rated from 105 to 125 hp across 1978–1985.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4" |
| Stroke | 3.5" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.143 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | diesel |
| Advertised HP | 105–125 hp |
| Years | 1978–1985 |
| Bore/stroke character | 1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,500 ft/min — conservative for a street engine |
| Displacement per cylinder | 43.8 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 |
|---|---|---|
| 1978 | 120 hp | LF9 |
| 1979 | 120 hp | LF9 |
| 1980 | 105 hp | LF9 |
| 1980 | 125 hp | LF9 |
| 1981 | 105 hp | LF9 |
| 1981 | 125 hp | LF9 |
| 1982 | 105 hp | LF9 |
| 1983 | 105 hp | LF9 |
| 1984 | 105 hp | LF9 |
| 1985 | 105 hp | LF9 |