These S&S® Super Stock® high performance cylinder heads are designed for 1999-'05 engines with stock crankcase. They work well with engines of stock displacement, but are ideal for somewhat larger stroker or big bore engines up to 110". The 79cc combustion chamber provides a slightly higher than stock, which makes most performance cams work better. Machined for S&S® compression releases. The large 1.940" intake and 1.575" exhaust valves maintain port velecity for good low and midrange response, but supply enough air for stock and slightly larger engines to perform to their full potential. 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.