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Buick LD5 specs: 231 ci (3.8L) 6-cylinder, 3.799 x 3.402 in (96.5 x 86.4 mm) bore and stroke. Rated 105-115 hp, 1977–1987. Used in the Oldsmobile Cutlass.
The Buick V6 (LD5) 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 3 engines in the Buick V6 family, all of them 231 ci — the differences between them are in compression, heads and rating, not displacement. 15 factory variants share these dimensions, rated from 105 to 115 hp across 1977–1987.
| Displacement | 231 ci / 3.8 L |
|---|---|
| Bore | 3.7992" |
| Stroke | 3.4016" |
| Cylinders | 6 |
| Configuration | V6 |
| Bore/stroke ratio | 1.117 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 105–115 hp |
| Years | 1977–1987 |
| 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 |
|---|---|---|
| 1977 | 105 hp | LD5 |
| 1978 | 105 hp | LD5 |
| 1979 | 105 hp | LD5 |
| 1979 | 115 hp | LD5 |
| 1980 | 110 hp | LD5 |
| 1980 | 115 hp | LD5 |
| 1981 | 110 hp | LD5 |
| 1982 | 110 hp | LD5 |
| 1982 | 115 hp | LD5 |
| 1983 | 110 hp | LD5 |
| 1983 | 112 hp | LD5 |
| 1984 | 110 hp | LD5 |
| 1985 | 110 hp | LD5 |
| 1986 | 110 hp | LD5 |
| 1987 | 110 hp | LD5 |