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Pontiac 350ci specs: 350 ci (5.7L) 8-cylinder, 3.80 x 3.85 in (96.5 x 97.8 mm) bore and stroke, 9.611:1 compression. Rated 145-165 hp, 1975. OHV.
The Pontiac 350ci is close to square: 3.8" bore against 3.85" stroke, within 1.3%, which splits the difference between a high-revving layout and a torque layout. The 3.85" stroke puts mean piston speed at 4,000 ft/min around 6,250 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.659 is in the range most production engines fall in. Each of the 8 cylinders displaces 43.8 ci (717 cc).
9.611:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 13 engines in the Pontiac 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated from 145 to 165 hp in 1975.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 3.8" |
| Stroke | 3.85" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9.611:1 |
| Rod length | 6.387" |
| Rod ratio | 1.659 |
| Bore/stroke ratio | 0.987 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 145–165 hp |
| Years | 1975 |
| Bore/stroke character | 0.987 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,850 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.659 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 43.8 ci |
| Static compression | 9.611:1 — in the range that usually runs on pump premium |
| Intake valve diameter | 1.88" |
|---|---|
| Exhaust valve diameter | 1.555" |
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 | 145 hp | — |
| 1975 | 165 hp | — |