Ross Racing Pistons supplied these top-quality forged aluminum slugs with valve reliefs that provide much needed piston-to-valve clearance. This becomes a necessity when running aggressive cam profiles. The pistons have a compression height of 1.260 inches and a diameter of 4.095, which give a clearance of .005 with the 4.1-inch cylinder bore. The final compression ratio, when combined with the 54cc chamber cylinder heads, works out to a healthy 12:1 ratio. ARE selected Total Seal rings for this application.