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Plymouth 413 4BBL specs: 413 ci (6.8L) 8-cylinder, 4.126 x 3.902 in (104.8 x 99.1 mm) bore and stroke, 10:1 compression. Rated 340 hp. OHV.
The Plymouth 413 4BBL 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).
10:1 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, the smallest at 413 ci. Factory fitments include the Plymouth Fury.
| Displacement | 413 ci / 6.8 L |
|---|---|
| Bore | 4.126" |
| Stroke | 3.9016" |
| Cylinders | 8 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.058 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 340 hp |
| 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 |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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