VVEL varies valve lift by the eccentric control shaft inside the rocker arm. One primary intake rocker arm corresponds to each secondary intake rocker arm. A similar arrangement transfers the motion via another roller tip to a second rocker arm. The top end of the lifter pushes on the rocker arm, which opens the valve. This arrangement caused the outer exhaust valves to have a rather long rocker arm. Current automotive design favors rocker arm ratios of about 1.5&colon;1 to 1.8&colon;1. The rocker arm design was originally used by the Ford 385 series engines. This pushes the rocker arm up and down about the trunnion pin or rocker shaft. Each valve pair is controlled by one rocker arm, which is operated by the camshaft. Regardless of number, the camshaft usually operates the valves indirectly via a rocker arm. The primary exhaust rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation.