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Pontiac L34 specs: 350 ci (5.7L) 8-cylinder, 4.057 x 3.385 in (103 x 86 mm) bore and stroke. Rated 170 hp, 1975–1980. Used in the Oldsmobile Cutlass.
The Pontiac 350ci (L34) is oversquare — the 4.057" bore exceeds the 3.385" stroke by 19.9% — 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. Each of the 8 cylinders displaces 43.8 ci (717 cc).
It is one of 20 engines in the Pontiac 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 4 factory variants share these dimensions, rated at 170 hp across 1975–1980.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4.057" |
| Stroke | 3.385" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 7.9–8.5:1 (published figures vary) |
| Bore/stroke ratio | 1.199 |
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 170 hp |
| Years | 1975–1980 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1977 | LM1 net | 170 @ 3800 | 270 lb-ft @ 2400 | 8.5:1 | 280° / 288° | 0.390" / 0.410" | 113° |
Factory specification sheet. Durations are the factory's advertised figures at the basis printed on the sheet, not duration at .050" lift; lobe separation is calculated from the printed valve timing.
| Bore/stroke character | 1.199 — 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 |
| 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 |
|---|---|---|
| 1975 | — | L34 |
| 1977 | 170 hp | L34 |
| 1979 | — | L34 |
| 1980 | — | L34 |
10 factory vehicles, 1972–1980. Each year opens that model's engine table.