For budget or stock-style rebuilds, it's hard to beat the value of Sealed Power cast pistons. They are made from high-quality aluminum alloys and feature a carefully controlled casting, heat-treating, and CNC-machining process. And, because they're designed and manufactured to exceed OEM specs, they'll provide improved reliability, performance, and a long service life. Pontiac 400 6.6L (1967-1979) Flat Top Four Valve Relief Piston. Bore (in): 4.120 in. Bore (mm): 104.648mm Piston Style: Flat top, with four valve reliefs Piston Material: Cast aluminum Wrist Pin Style: Press-fit Pin Diameter (in): 0.980 in. Piston Ring Thickness: 5/64 in. x 5/64 in. x 3/16 in.