The AMC 150/2.5 L engine has a bore of 3.875 in (98.4 mm) and a stroke of 3.1875 in (80.96 mm). The head features a combustion chamber and port design that was later used on the 4.0 L — the 2.5 L I-4 head lost two cylinders in its center, juxtaposed to the six-cylinder engines. The 2.5 engine also features five main bearings and eight overhead valves.
Instead of the standard AMC bell housing bolt pattern, AMC/Jeep engineers adopted the General Motors small V6 and four-cylinder bolt pattern (commonly used with GM's transverse-mounted powerplants) for their new engine, because the new AMC 2.5 replaced the four-cylinder engines that had been purchased from GM; and because AMC continued to buy the 2.8 L V6 from GM until the 4.0 L I6 was introduced in 1987. The four-cylinder and V6 shared the same drivetrain components, whereas stronger transmissions were needed for the new 4.0 L.
The AMC I4 first appeared in 1984 model year with the new XJ Cherokee. In 1986 the head went under a minor revision, the head bolts were increased from 7/16 to 1/2 inch. From 1997 to 2002 it was marketed as the "Power-Tech I4".[3] It was produced through 2002 for the Jeep Wrangler, as well as for the Dodge Dakota pickup that also featured the AMC/Jeep designed four-cylinder as its standard engine from 1996 through 2002.
This lightweight engine is similar to its "big brother" 4.0 L, and although not powerful, it is durable with no reliability issues.[4]
Output the final year was 121 hp (90 kW; 123 PS) at 5400 rpm and 145 lb·ft (197 N·m) of torque at 3250 rpm using sequential multiple-port fuel injection (MPFI). For comparison, the 258 I6 provided 112 hp (84 kW; 114 PS) at 3200 rpm and 210 lb·ft (280 N·m) of torque at 2000 rpm in its final year with the computer-controlled carburetor.
For several years, the engine was detuned for the Wrangler; from at least 1992-1995, it produced 130 hp (97 kW; 132 PS) and 149 lb·ft (202 N·m) of torque with 9.2:1 compression in the Cherokee and Comanche[WIKI]
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