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Oldsmobile L27 specs: 231 ci (3.8L) 6-cylinder, 3.799 x 3.402 in (96.5 x 86.4 mm) bore and stroke. Rated 170 hp, 1991–1994. Used in the Buick Regal. OHV.
The Oldsmobile 231ci (L27) is oversquare — the 3.7992" bore exceeds the 3.4016" stroke by 11.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.4016" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 38.5 ci (631 cc).
It is one of 12 engines in the Oldsmobile 231ci family, all of them 231 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated at 170 hp across 1991–1994.
| Displacement | 231 ci / 3.8 L |
|---|---|
| Bore | 3.7992" |
| Stroke | 3.4016" |
| Cylinders | 6 |
| Configuration | V6 |
| Compression ratio | 8.5–9:1 (published figures vary) |
| Bore/stroke ratio | 1.117 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-6-5-4-3-2 |
| Advertised HP | 170 hp |
| Years | 1991–1994 |
| Bore/stroke character | 1.117 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,402 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.5 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 |
|---|---|---|
| 1991 | 170 hp | L27 |
| 1994 | 170 hp | L27 |
9 factory vehicles, 1990–1995. Each year opens that model's engine table.