See other engines in this family
Jeep EPE specs: 150 ci (2.5L) 4-cylinder, 3.875 x 3.188 in (98.4 x 81 mm) bore and stroke, 9.1:1 compression. Rated 120 hp. OHV. Rod ratio and piston speed.
The Jeep AMC Straight-4 (EPE) is oversquare — the 3.875" bore exceeds the 3.1875" stroke by 21.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.1875" stroke does not reach 4,000 ft/min of mean piston speed until about 7,550 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 37.5 ci (615 cc).
9.1:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
Factory fitments include the Cherokee XJ, Wrangler YJ, Wrangler TJ.
| Displacement | 150 ci / 2.5 L |
|---|---|
| Bore | 3.875" |
| Stroke | 3.1875" |
| Cylinders | 4 |
| Compression ratio | 9.1:1 |
| Bore/stroke ratio | 1.216 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 120 hp |
| Bore/stroke character | 1.216 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,188 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.5 ci |
| Static compression | 9.1:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.