JE Pistons Ultra Series GM Gen III/IV LS 4.125in Bore/4in Stroke Set of 8 Pistons

JE Pistons is well-known for making some of the strongest pistons available, and their Ultra Series is a prime example of that. If you're building a serious GM Gen III or Gen IV LS engine, especially one that's going to see boost or nitrous, these pistons are built to handle the extreme cylinder pressures you'll encounter. They're designed to be a direct fit for a 4.125-inch bore with a 4-inch stroke, giving you a solid foundation for a high-horsepower build.

What sets these Ultra Series pistons apart is JE's proprietary Aligned Grain Flow forging technology. This process maximizes the tensile strength of the aluminum, making them incredibly robust for demanding engine environments. You'll also find custom-level features like a thermal barrier crown coating, which is a ceramic-based material that reflects heat back into the combustion chamber. This helps keep piston crown temperatures down and can improve how efficiently exhaust gases are scavenged. The pistons also come with a skirt coating to reduce friction and wear on the cylinder walls, which also helps quiet things down, especially during a cold start. For added reliability in high-RPM, high-boost situations, they include lateral gas ports to help maintain a strong seal on the top compression ring.

This set includes eight pistons, each equipped with high-strength, thick-wall wrist pins manufactured by Trend Performance in the USA. The pin oiling is also optimized to ensure everything stays well-lubricated, reducing heat and friction. Every feature on these pistons is geared towards high-horsepower racing engines, and they are proudly made 100% in the USA. Please note that these pistons are not CARB approved and cannot be shipped to California.