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Plymouth B (1959–1966) specs: 361 ci (5.9L) 8-cylinder, 4.125 x 3.375 in (104.8 x 85.7 mm) bore and stroke. Rated 265-310 hp, 1959–1966.
The Plymouth B (1959–1966) is oversquare — the 4.125" bore exceeds the 3.375" stroke by 22.2% — 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 45.1 ci (739 cc).
It is one of 10 engines in the B family, sitting between the 350 ci and 400 ci members. 9 factory variants share these dimensions, rated from 265 to 310 hp across 1959–1966.
| Displacement | 361 ci / 5.9 L |
|---|---|
| Bore | 4.125" |
| Stroke | 3.375" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9–10.1:1 (published figures vary) |
| Bore/stroke ratio | 1.222 |
| 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 | 265–310 hp |
| Years | 1959–1966 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1959 | gross | 305 @ 4600 | 400 lb-ft @ 2800 | 10.1:1 | — | — | — |
| 1960 | gross | 305 @ 4800 | 395 lb-ft @ 3000 | 10:1 | — | — | — |
| 1961 | gross | 305 | — | 9:1 | — | — | — |
| 1962 | gross | 305 @ 4800 | 395 lb-ft @ 3000 | 9:1 | — | — | — |
| 1963 | gross | 265 @ 4400 | 380 lb-ft @ 2400 | 9:1 | — | — | — |
| 1964 | gross | 265 @ 4400 | 380 lb-ft @ 2400 | 9:1 | — | — | — |
| 1965 | gross | 265 @ 4400 | 380 lb-ft @ 2400 | 9:1 | 252° | 0.392" / 0.390" | 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 | 1.222 — 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 | 45.1 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 |
|---|---|---|
| 1959 | 305 hp | — |
| 1960 | 305 hp | — |
| 1960 | 310 hp | — |
| 1961 | 305 hp | — |
| 1962 | 305 hp | — |
| 1963 | 265 hp | — |
| 1964 | 265 hp | — |
| 1965 | 265 hp | — |
| 1966 | 265 hp | — |
2 factory vehicles, 1959–1966. Each year opens that model's engine table.