JE Pistons Ultra Series GM Gen III/IV LS 4.005in Bore/4in Stroke Set of 8 Pistons

When you're building a serious GM LS Gen III or IV engine, especially one that's going to see boost or nitrous, you need pistons that can handle the pressure. This set of eight Ultra Series pistons from JE Pistons is built for those demanding applications. They feature JE's proprietary Aligned Grain Flow forging technology, which gives them exceptional tensile strength to stand up to the extreme cylinder pressures you'll encounter in high-horsepower builds.

These aren't just basic pistons; they come with custom-level features right out of the box. You get a thermal barrier crown coating that reflects heat, helping to keep piston crown temperatures down and improving how exhaust gases are scavenged. The skirts are coated to reduce friction and wear on both the piston and cylinder walls, which also helps quiet things down, especially when the engine is cold. Plus, lateral gas ports are included to help maintain a solid ring seal, even at high RPMs and under significant boost. The set also includes strong, thick-wall wrist pins from Trend Performance, designed specifically for high-performance and power-adder engines, and optimized pin oiling ensures everything stays well-lubricated.

Every part of this piston set is designed to perform in high-horsepower racing engines, and they are all made 100% in the USA. Keep in mind that this kit is not CARB approved and cannot be shipped to California. You'll also want to check the manufacturer's specifications for details on the dome volume and pin size to ensure they match your specific build requirements.