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Plymouth RB (1962) specs: 413 ci (6.8L) 8-cylinder, 4.126 x 3.902 in (104.8 x 99.1 mm) bore and stroke. Rated 385-420 hp, 1962. Used in the Dodge Dart. OHV.
The Plymouth RB (1962) is oversquare — the 4.126" bore exceeds the 3.9016" stroke by 5.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.9016" stroke puts mean piston speed at 4,000 ft/min around 6,150 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 51.6 ci (846 cc).
It is one of 25 engines in the RB family, the smallest at 413 ci. 3 factory variants share these dimensions, rated from 385 to 420 hp in 1962.
| Displacement | 413 ci / 6.8 L |
|---|---|
| Bore | 4.126" |
| Stroke | 3.9016" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.058 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 385–420 hp |
| Years | 1962 |
| Bore/stroke character | 1.058 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,902 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 51.6 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 |
|---|---|---|
| 1962 | 385 hp | — |
| 1962 | 410 hp | — |
| 1962 | 420 hp | — |