Stock Rubbing Rocker Arms and Performance Roller Rocker Arms
Cam manufacturers refer to their camshafts by the valve lift not the camshaft’s lobe lift. The actual camshaft lobe lift is multiplied by the rocker arm ratio to obtain the valve lift. Valve lift is almost always greater than cam lobe lift. The exception is the 1936 to 1947 Knuckledhead. The Knucklehead’s rocker arm has a 1:1 ratio, whereby cam lobe lift and actual valve lift are the same. Valve lift is how far the valve extends into the combustion chamber.