These S&S® Super Stock® high performance cylinder heads are designed specifically for S&S® T-Series complete engines and 1999-'05 engines with S&S® 4-1/4" bore Hot Set Up Kit installed. 2.000" intake and 1.605" exhaust valves coupled with S&S® ports, supply plenty of air for these big motors. Not machined for S&S® compression releases. The manifold mounting surface is machined to stock dimensions, so a special manifold/throttle body is required for engines that are not stock height. Machined for vacuum crankcase breathing, not compatible with stock style air cleaners. S&S® High performance valve springs allow the installation of camshafts with up to .650" lift. Compatible with stock rocker boxes, exhaust, and intake manifolds. Black wrinkle powder coat finish matches silver engine components.