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Plymouth B (1960–1971) specs: 383 ci (6.3L) 8-cylinder, 4.25 x 3.375 in (108 x 85.7 mm) bore and stroke. Rated 270-340 hp, 1960–1971.
The Plymouth B (1960–1971) is oversquare — the 4.25" bore exceeds the 3.375" stroke by 25.9% — 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. A rod ratio of 1.884 is long by production standards — less side-load on the cylinder wall and gentler piston acceleration around TDC, the geometry that tolerates high RPM. Each of the 8 cylinders displaces 47.9 ci (785 cc).
It is one of 10 engines in the B family, sitting between the 350 ci and 400 ci members. 28 factory variants share these dimensions, rated from 270 to 340 hp across 1960–1971.
| Displacement | 383 ci / 6.3 L |
|---|---|
| Bore | 4.25" |
| Stroke | 3.375" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.5–10.1:1 (published figures vary) |
| Rod length | 6.358" |
| Rod ratio | 1.884 |
| Bore/stroke ratio | 1.259 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 270–340 hp |
| Years | 1960–1971 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1960 | gross | 325 @ 4600 | 425 lb-ft @ 2800 | 10.1:1 | — | — | — |
| 1960 | gross | 330 @ 4800 | 460 lb-ft @ 2800 | 10.1:1 | — | — | — |
| 1961 | gross | 325 @ 4600 | 425 lb-ft @ 2800 | 10:1 | — | — | — |
| 1961 | gross | 330 @ 4800 | 460 lb-ft @ 2800 | 10:1 | — | — | — |
| 1963 | gross | 330 @ 4600 | 425 lb-ft @ 2800 | 10:1 | — | — | — |
| 1964 | gross | 330 @ 4600 | 425 lb-ft @ 2800 | 10:1 | — | — | — |
| 1965 | gross | 270 @ 4400 | 390 lb-ft @ 2800 | 9.2:1 | — | — | — |
| 1965 | gross | 330 @ 4600 | 425 lb-ft @ 2800 | 10:1 | — | — | — |
| 1967 | gross | 270 @ 4400 | 390 lb-ft @ 2800 | 9.2:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1967 | gross | 325 @ 4800 | 425 lb-ft @ 2800 | 10:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1968 | gross | 290 @ 4400 | 390 lb-ft @ 2800 | 9.2:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1968 | gross | 300 @ 4200 | 400 lb-ft @ 2400 | 10:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1968 | gross | 330 @ 5000 | 425 lb-ft @ 3200 | 10:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1968 | gross | 335 @ 5200 | 425 lb-ft @ 3400 | 10:1 | 256° / 260° | 0.425" / 0.435" | 113° |
| 1969 | gross | 290 @ 4400 | 390 lb-ft @ 2800 | 9.2:1 | 256° / 260° | 0.425" / 0.437" | 113° |
| 1969 | gross | 330 @ 5000 | 425 lb-ft @ 3200 | 10:1 | — | — | — |
| 1969 | gross | 335 @ 5000 | 425 lb-ft @ 3400 | 10:1 | 268° / 284° | 0.450" / 0.465" | 115° |
| 1970 | gross | 290 | — | — | 256° / 260° | 0.425" / 0.435" | 113° |
| 1971 | gross | 275 @ 4400 | 375 lb-ft @ 2800 | 8.5:1 | — | — | — |
| 1971 | gross | 300 @ 4800 | 410 lb-ft @ 3400 | 8.5:1 | — | — | — |
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 | 1.259 — 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 |
| Rod ratio | 1.884 — long — less side loading on the cylinder wall, favours high RPM |
| Displacement per cylinder | 47.9 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 |
|---|---|---|
| 1960 | 325 hp | — |
| 1960 | 330 hp | — |
| 1961 | 325 hp | — |
| 1961 | 330 hp | — |
| 1961 | 340 hp | — |
| 1962 | — | — |
| 1963 | 330 hp | — |
| 1964 | 330 hp | — |
| 1965 | 270 hp | — |
| 1965 | 330 hp | — |
| 1966 | 270 hp | — |
| 1966 | 325 hp | — |
| 1967 | 270 hp | — |
| 1967 | 280 hp | — |
| 1967 | 325 hp | — |
| 1968 | 290 hp | — |
| 1968 | 300 hp | — |
| 1968 | 330 hp | — |
| 1968 | 335 hp | — |
| 1969 | 290 hp | — |
| 1969 | 330 hp | — |
| 1969 | 335 hp | — |
| 1970 | 290 hp | — |
| 1970 | 330 hp | — |
| 1970 | 335 hp | — |
| 1971 | — | — |
| 1971 | 275 hp | — |
| 1971 | 300 hp | — |
4 factory vehicles, 1960–1971. Each year opens that model's engine table.