If you don't have one of the old and trusty 4.2L- or 4.0L-equipped Jeeps you probably had one in the past or have a buddy with one. So what do you do when you want to get some more power from a used ...

Jeep’s 4.0-liter straight-six engine is iconic. Much like the Ford 300, it’s a down-and-dirty truck engine that stayed in production for decades. Also like the Ford 300, it can make a ton of power ...

Owing to its simplistic cam-in-block design, Jeep’s 4.0-liter straight-six is known for two things: Unflappable reliability and a lack of power. Its maximum of 190 horsepower and 235 pound-feet of ...