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Pontiac LM1 specs: 350 ci (5.7L) 8-cylinder, 4.00 x 3.48 in (101.6 x 88.4 mm) bore and stroke. Rated 165-170 hp, 1977–1979. Used in the Chevrolet Camaro.
The Pontiac 350ci (LM1) is oversquare — the 4" bore exceeds the 3.48" stroke by 14.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.48" stroke puts mean piston speed at 4,000 ft/min around 6,900 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. 5 factory variants share these dimensions, rated from 165 to 170 hp across 1977–1979.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4" |
| Stroke | 3.48" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.2–8.5:1 (published figures vary) |
| Bore/stroke ratio | 1.149 |
| Fuel type | gas |
|---|---|
| Advertised HP | 165–170 hp |
| Years | 1977–1979 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1978 | LM1 net | 170 @ 3800 | 270 lb-ft @ 2400 | 8.2:1 | 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 | 1.149 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,480 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 |
|---|---|---|
| 1977 | — | LM1 |
| 1978 | — | LM1 |
| 1978 | 170 hp | LM1 |
| 1979 | — | LM1 |
| 1979 | 165 hp | LM1 |
18 factory vehicles, 1969–1988. Each year opens that model's engine table.