The Edelbrock part # 77409 Victor 24° 340cc cylinder head features a rolled over deck, altered valve locations and partially CNC'd 199cc chambers for cost effective performance. The Edelbrock 77409 cylinder head comes complete with springs to suite mechanical roller camshafts. Mechanical roller cam springs include Manley dual-spring valve springs & titanium retainers good for up to .880" lift. The 340cc rectangle ports produce impressive flow and great power on competition big-blocks with 4.470" or larger bore. Exhaust port exits are raised .534". INSTALLATION NOTE: Matching stud girdle #7796 must be used with stud mounted rocker arms. Deck thickness: 9/16", rocker stud diameter: 7/16", pushrod diameter: 3/8" (width of slot in guide plate).