Valve spring kits are direct replacement no machining or rocker box clearance required Larger lift camshafts require valve guide machining for seal and retainer clearance .050" offset 10°, 5/16" steel valve locks, raises the valve spring retainer to gain .050" installed high without machining the cylinder head spring seat Up to .574" lift for 1984-2004 Big Twin, 1986-2003 Sportster and up to .700" lift for 2005-17 Twin cam