S&S Cycle Cams for Panhead, Shovelhead, & Harley-Davidson Evolution Engines - Manual (Page 7)

6 7
E Once the valve springs have been installed it is important to check for coil bind. With valve fully open, there must be a minimum of .060"
additional valve travel available before either the inner or outer valve springs are coil bound solid. If this clearance does not exist, the valves
must be sunk deeper in the head by grinding the valve seats. The typical installed valve spring height of 1.520" for panhead engines and
shovelhead engines, and 1.800" for Evolution® models should not be increased by more than .040".
F. Always check for clearance between the valve spring retainer and the inside face of the rocker arm. This is most critical when the valve is
fully closed. Rocker arms are designed to clear specific spring diameters so it is important that the proper rocker arm/retainer combination
is used. Insufficient clearance can also be the result of improper rocker arm geometry and/or incorrect valve stem length.