SB Ford 170cc Aluminum Cylinder Heads. 2.02" intake, 1.60" exhaust, 60cc combustion chambers. Manufactured from A356-T6 aluminum. Assembled with 1.47" OD springs for hydraulic roller cams up to .625" lift. Requires 7/16" stud rocker arms. Each pair comes assembled with a detailed flow sheet and assembly blueprint. Vacuum tested. Download Data here - DOWNLOAD Sold as pairs. NOTE: Not for use with factory pistons. Check piston to valve clearance in all applications.