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Ram 64 Hemi Apache specs: 392 ci (6.4L) 8-cylinder, 4.091 x 3.724 in (103.9 x 94.6 mm) bore and stroke, 10:1 compression. Rated 410 hp. OHV.
The Ram 64 Hemi Apache is oversquare — the 4.0906" bore exceeds the 3.7244" stroke by 9.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.7244" stroke puts mean piston speed at 4,000 ft/min around 6,450 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 49.0 ci (803 cc).
10:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 10 engines in the Hemi family, the largest at 392 ci. Factory fitments include the Ram 2500, Ram 3500, Ram Power Wagon and 1 other.
| Displacement | 392 ci / 6.4 L |
|---|---|
| Bore | 4.0906" |
| Stroke | 3.7244" |
| Cylinders | 8 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.098 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 410 hp |
| Bore/stroke character | 1.098 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,724 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 49.0 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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