Buick 401 Nailhead Pistons

This piston set is a direct replacement for the '59-'66 Buick 401 Nailhead, cast at a 4.1875-inch bore from a high-silicon aluminum alloy and finished on modern CNC equipment rather than older tooling. What makes the set Every set is precision balanced and weight-matched, with no more than an 8-gram spread between the lightest and heaviest piston, which matters for a smooth-running V8 at higher RPM. The rings supplied are a cast top ring paired with a cast second ring. Before you order Confirm your block is a genuine 401 Nailhead from this model-year range and that your bore matches 4.1875 inches before ordering, since piston sets like this are machined to a specific bore rather than a universal size. A qualified engine builder should handle fitting and ring gap checks during assembly. Common questions What alloy are these pistons? High-silicon A-332 cast aluminum, machined on CNC equipment. How closely matched is the set? Within 8 grams from the lightest piston to the heaviest.