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Plymouth E specs: 426 ci (7.0L) 8-cylinder, 4.25 x 3.75 in (108 x 95.3 mm) bore and stroke, 10.3:1 compression. Rated 365 hp. OHV. Rod ratio and piston speed.
The Plymouth RB (E) is oversquare — the 4.25" bore exceeds the 3.75" stroke by 13.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.75" 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 53.3 ci (873 cc).
10.3:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 25 engines in the RB family, sitting between the 413 ci and 440 ci members. Factory fitments include the Plymouth Sport Fury, Plymouth Belvedere.
| Displacement | 426 ci / 7 L |
|---|---|
| Bore | 4.25" |
| Stroke | 3.75" |
| Cylinders | 8 |
| Compression ratio | 10.3:1 |
| Bore/stroke ratio | 1.133 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 365 hp |
| Bore/stroke character | 1.133 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,750 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 53.3 ci |
| Static compression | 10.3:1 — in the range that usually runs on pump premium |
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