We got a lot of questions about the ISX/QSX engines and what is the proper piston & liner kit to use for their engines. There have been many updates to these engines over the years and have evolved to improve engine longevity and performance. You can check our post on proper liner id for further information. Interstate Mcbee does a good job of summarizing and visualizing the progression below. Something that is important to understand is that depending on your engine you may have several different options available that will work for you. Usually you want to go with the most advanced option available but ALWAYS make sure you use the same set-up for all 6 cylinders. Shoot us a message below and we can help you determine the best options available for your engine and get you back on the road quickly and in the most cost efficient manner.