AMC/Chrysler/Jeep 4.0 Engine The Jeep 4.0 isn't only a legend in the Jeep world, but also the automotive industry as a whole. AMC developed this engine prior to Chrysler buying them out in 1987. It's a strong and reliable engine, however, the 4.0L straight-6 is also known for a lack of power. Regardless, the 4.0 is an excellent all around engine that many appreciate to this … [Read more...] about Jeep 4.0 Straight-Six Engine