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Plymouth RB (1967–1976) specs: 440 ci (7.2L) 8-cylinder, 4.319 x 3.752 in (109.7 x 95.3 mm) bore and stroke. Rated 255-390 hp, 1967–1976.
The Plymouth RB (1967–1976) is oversquare — the 4.3189" bore exceeds the 3.752" stroke by 15.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.752" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 55.0 ci (901 cc).
It is one of 25 engines in the RB family, the largest at 440 ci. 12 factory variants share these dimensions, rated from 255 to 390 hp across 1967–1976.
| Displacement | 440 ci / 7.2 L |
|---|---|
| Bore | 4.3189" |
| Stroke | 3.752" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.151 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 255–390 hp |
| Years | 1967–1976 |
| Bore/stroke character | 1.151 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,752 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 55.0 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 |
|---|---|---|
| 1967 | 375 hp | — |
| 1968 | 375 hp | — |
| 1969 | 375 hp | — |
| 1970 | 375 hp | — |
| 1970 | 390 hp | — |
| 1971 | 370 hp | — |
| 1971 | 385 hp | — |
| 1972 | 280 hp | — |
| 1973 | 280 hp | — |
| 1974 | 275 hp | — |
| 1975 | 260 hp | — |
| 1976 | 255 hp | — |