In contrast, some older OHV (pushrod) engines had redlines as low as 4800 rpm, mostly due to the engines being designed and built for low-end power and economy during the late 1960s all the way to the early 1990s. One main reason OHV engines have lower redlines is valve float. At high speeds, the valve spring simply cannot keep the tappet or roller on the camshaft. After the valve opens, the valve spring does not have enough force to push the mass of the rocker arm, pushrod, and lifter down on the cam before the next combustion cycle. Overhead cam engines eliminate many of the components and moving mass, used on OHV engines. Lower redlines, however, do not necessarily mean low performance.