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Pontiac L30 specs: 350 ci 8-cylinder, 3.875 x 3.75 in (98.4 x 95.3 mm) bore and stroke. Rated 150-255 hp, 1970–1974. Used in the Pontiac Catalina.
The Pontiac 350ci (L30) is close to square: 3.875" bore against 3.75" stroke, within 3.3%, which splits the difference between a high-revving layout and a torque layout. The 3.75" stroke puts mean piston speed at 4,000 ft/min around 6,400 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 20 engines in the Pontiac 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 9 factory variants share these dimensions, rated from 150 to 255 hp across 1970–1974.
| Displacement | 350 ci |
|---|---|
| Bore | 3.875" |
| Stroke | 3.75" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8–8.8:1 (published figures vary) |
| Bore/stroke ratio | 1.033 |
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 150–255 hp |
| Years | 1970–1974 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1970 | L30 gross | 255 | 355 lb-ft | 8.8:1 | — | — | — |
| 1971 | L30 gross | 250 @ 4400 | 350 lb-ft @ 2400 | 8:1 | 269° / 277° | 0.377" / 0.413" | — |
| 1972 | L30 net | 160 @ 4400 | 270 lb-ft @ 2000 | 8:1 | — | — | — |
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 | 1.033 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,750 ft/min — in the range typical of performance street engines |
| 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 |
|---|---|---|
| 1970 | 255 hp | L30 |
| 1971 | 250 hp | L30 |
| 1972 | — | L30 |
| 1972 | 160 hp | L30 |
| 1973 | — | L30 |
| 1973 | 150 hp | L30 |
| 1974 | — | L30 |
| 1974 | 155 hp | L30 |
| 1974 | 170 hp | L30 |
5 factory vehicles, 1970–1976. Each year opens that model's engine table.