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Buick L80 specs: 403 ci (6.6L) 8-cylinder, 4.351 x 3.385 in (110.5 x 86 mm) bore and stroke. Rated 185 hp, 1978–1979. Used in the Pontiac Firebird. OHV.
The Buick 403ci (L80) is oversquare — the 4.351" bore exceeds the 3.385" stroke by 28.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.385" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.773 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 50.4 ci (825 cc).
It is one of 2 engines in the Buick 403ci family, all of them 403 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated at 185 hp across 1978–1979.
| Displacement | 403 ci / 6.6 L |
|---|---|
| Bore | 4.351" |
| Stroke | 3.385" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 6.002" |
| Rod ratio | 1.773 |
| Bore/stroke ratio | 1.285 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 185 hp |
| Years | 1978–1979 |
| Bore/stroke character | 1.285 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,385 ft/min — conservative for a street engine |
| Rod ratio | 1.773 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 50.4 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 | 185 hp | L80 |
| 1979 | 185 hp | L80 |