The Jeep 4.0L inline-six was the last true Jeep/AMC engine design before Chrysler bought everything and folded it into the Pentastar family. It was the final derivative of the old 4.2 inline-six and debuted in the 1987 model year. It’s last year in an American Jeep would be 2006, when the TJ Wrangler ended production. But you’re not here for a history lesson, so for the complete background on the 4.0L click HERE.

What does this have to do with heat?

The 4.0L is a massive hunk of cast iron American greatness. But all that cast iron means it’s a giant heat source under the hood, and once it gets hot it holds that heat for a while. And everything around it underhood soaks up all that heat, which can negatively affect performance, reliability, and component life. But with some application of Heatshield Products thermal barriers, the amo

Read more »