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Jeep EZH specs: 345 ci (5.7L) 8-cylinder, 3.917 x 3.579 in (99.5 x 90.9 mm) bore and stroke, 10.5:1 compression. Rated 360 hp. Rod ratio and piston speed.
The Jeep HEMI (EZH) is oversquare — the 3.9173" bore exceeds the 3.5787" stroke by 9.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.5787" stroke puts mean piston speed at 4,000 ft/min around 6,700 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.1 ci (707 cc).
10.5:1 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 8 engines in the HEMI family, the smallest at 345 ci. Factory fitments include the Grand Cherokee WK2, Commander XK, Wagoneer WS and 2 others.
| Displacement | 345 ci / 5.7 L |
|---|---|
| Bore | 3.9173" |
| Stroke | 3.5787" |
| Cylinders | 8 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 1.095 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 360 hp |
| Bore/stroke character | 1.095 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,579 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 43.1 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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