Jeep Engine Specs - 4.0 LITER, OHV, 12-VALVE SMPI POWER TECH I-6

The Jeep 4.0 liter PowerTech Straight-Six engine provided exciting acceleration in Jeep Wranglers for years, with excellent torque. In the Cherokee it did well, in the Grand Cherokee it was a bit sluggish due to the weight of that vehicle.

When the 4.0 first came out, AMC was using two six cylinder engines, a troublesome 2.8 liter V6 from General Motors (with a problematic Ford carburetor) and AMC's own 258 CID straight-six, with 4.2 liters of displacement, that the 4.0 itself was based on. The 4.2 was used in the CJ7, and the YJ. While the 4.2 and 2.8 were both relatively strong for their day - the 4.0 beat just about all competing engines, including those of Japanese automakers. (The 4.2 produced about 112 hp in 1990, the 2.8 about 120 hp, and the 2.5 about 117 hp - torque was naturally higher in the 4.2).

When the 4.0 did burst onto the scene, it had a full 180 horsepower in the Wrangler and, in the Cherokee, it started out with 177 hp. The Cherokee's version made 190 hp starting in 1991. The YJ didn't get the 4.0 until the 1990s (it was still using the old 258 I6). When the YJ did get the 4.0, it only made 181HP due to the restrictive exhaust.

When the it was introduced, the 4.0 I6 made more power than the Ford 302 V8, Chevy 305, Chrysler 318, and AMC 360. It also was way more powerful than any 6 cylinder engines the Japanese were putting in their trucks... and had comparable or better fuel economy. It left the V6 engines from Ford, GM and Chrysler in the dust.