2.5L I-4
From JeepForum.com Community Jeep Wiki
The AMC (American Motors Corporation) straight-4 engine is used by a number of AMC, Jeep and Dodge vehicles from 1984 through 2002.
2.5L Straight-4
The 2.5L inline-4 is a shortened version of the 4.2L 258 I-6 engine bored to 3.88 in (99 mm) and de-stroked to 3.19 in (81 mm). The block is basically the same as the 4.2L I-6 with a larger bore and the two center cylinders removed. The head featured a new combustion chamber and port design which was later used on the 4.0L I-6 -- the 2.5L I-4 head is stretched by two cylinders in the center.
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 2.5 replaced four-cylinder engines which had been purchased from GM; and because AMC continued to buy the 2.8L V6 from GM until the 4.0L I-6 was introduced in 1987. The four-cylinder and V6 shared the same drivetrain components, whereas stronger transmissions were needed for the 4.0L I-6.
The AMC I-4 appeared in 1984 with the new XJ Cherokee and was produced through 2002 for the Jeep Wrangler and Dodge Dakota pickup, which used the AMC/Jeep designed four since 1996.
Specifications
| Bore x Stroke | 3.88" x 3.19" |
| Displacement | 150ci (2.5L) |
| Horsepower Output (final year) | 123 HP SAE (89 kW) @ 5,400 rpm |
| Torque Output (final year) | 145 ft lbs (197 N·m) @ 3,250 rpm |
| Valvetrain | Eight overhead valves |
| Main bearings | Five |
| Compression ratio | 9.1:1 to 9.2:1 depending on year |
| Firing Order | 1-3-4-2 Clockwise (see image) |
Notes
The final production year used sequential mulitple-port fuel injection. For comparison, the 4.2L I-6 produced 112 HP @ 3,200 rpm and 210 ft lbs of torque @ 2,000 rpm in its final year with the computer controlled carburetor.
For several years, the engine was detuned for the Wrangler; from at least 1992 to 1995, it produced 130 horsepower and 149 ft lbs of torque with 9.2:1 compression in the Cherokee and Comanche.
