Welcome to Jeep Engines-3rd Edition. This performance book has been prepared as a guide for those enthusiasts who are interested in everything from mild performance gains to building highly competitive racing vehicles and is intended to compliment the service manual for your particular vehicle and/or engine. Therefore, to avoid any possible problems and/or headaches, Mopar Performance Parts highly recommends that the proper service manual for your vehicle and/or engine be obtained. This performance book builds on the service manual information. Service manuals tell you how to take your engine apart and put it back together; Jeep Engines-3rd Edition tells you how to modify your engine and increase its performance. If you find that you need further assistance or have any performance and/or modification questions you would like to ask, you can contact Mopar Performance Parts Technical Assistance. The primary emphasis of this book is on the 4.0L Power Tech In-Line 6 cylinder engine, the 4.2L In-Line 6 cylinder engine, the 2.5L Power Tech In-Line 4 cylinder engine, and the 360 AMC V-8 engine. The 2.46L In-Line 4 cylinder engine is also covered, but because of the limited number of performance parts available, it is discussed only briefly. We have also included a special chapter which highlights our new all-aluminum 4.7L V-8 engine that debuted in 1999. This new engine is certain to play an important role in our future Jeep performance parts program. Magnum engines have their own book; therefore, they are not covered in this book. Note: For complete Magnum V-10, V-8, V-6, and 4- cylinder engine information, refer to Magnum Engines (P4876668), as well as the appropriate service manual.