The most common forged alloys are 2618 (a low-silicon aluminum), and 4032 (an alloy with around 11-percent silicon). 4032 is typically the alloy of choice in street/strip applications. It’s selected because of the capability of tighter piston-to-wall clearance gained by the lower expansion rate. Another benefit is longer skirt and ring-belt life offered by the greater wear resistance of the higher-silicon alloy. The 2618 alloy does give up some of the benefits achieved from silicon, it is commonly agreed to be the best piston material for brutal all-out race applications. The lower-silicon alloy has a higher density rating and tensile strength than 4032, and has a much greater ductility and fracture resistance. 2618 alloy pistons are designed to be racing pistons. Don’t install these in your car or truck, and expect to travel 100,000-plus miles. If the plan calls for serious nitrous, boost, or rpm, and bulletproof is what you are after, a 2618 piston is the right choice.