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Plymouth B specs: 400 ci (6.6L) 8-cylinder, 4.342 x 3.375 in (110.3 x 85.7 mm) bore and stroke, 8.2:1 compression. Rated 190-255 hp, 1972.
The Plymouth B is oversquare — the 4.342" bore exceeds the 3.375" stroke by 28.7% — 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 50.0 ci (819 cc).
8.2:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 27 engines in the B family, the largest at 400 ci. 2 factory variants share these dimensions, rated from 190 to 255 hp in 1972.
| Displacement | 400 ci / 6.6 L |
|---|---|
| Bore | 4.342" |
| Stroke | 3.375" |
| Cylinders | 8 |
| Compression ratio | 8.2:1 |
| Bore/stroke ratio | 1.287 |
| Valvetrain | OHV |
|---|---|
| Valves per cylinder | 2 |
| Induction | 2-bbl |
| Advertised HP | 190–255 hp |
| Years | 1972 |
| Bore/stroke character | 1.287 — 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 | 50.0 ci |
| Static compression | 8.2:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 1972 | 190 hp | — |
| 1972 | 255 hp | — |