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Plymouth B (1958) specs: 350 ci (5.7L) 8-cylinder, 4.063 x 3.375 in (103.2 x 85.7 mm) bore and stroke, 10:1 compression. Rated 305-315 hp, 1958.
The Plymouth B (1958) is oversquare — the 4.0625" bore exceeds the 3.375" stroke by 20.4% — a layout that favors airflow and RPM over leverage at the crank. The 3.375" 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).
10:1 is in the range that usually runs on pump premium.
It is one of 10 engines in the B family, the smallest at 350 ci. 2 factory variants share these dimensions, rated from 305 to 315 hp in 1958.
| Displacement | 350 ci / 5.7 L |
|---|---|
| Bore | 4.0625" |
| Stroke | 3.375" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.204 |
| Valvetrain | OHV |
|---|---|
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 305–315 hp |
| Years | 1958 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1958 | gross | 305 @ 5000 | 370 lb-ft @ 3600 | 10:1 | 252° | — | 111° |
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 | 1.204 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,375 ft/min — conservative for a street engine |
| Displacement per cylinder | 43.8 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| 1958 | 305 hp | — |
| 1958 | 315 hp | — |
1 factory vehicle, 1958. Each year opens that model's engine table.