Camshafts and Valve Depressors

Each cylinder head has twin overhead camshafts with a large-diameter base circle, resulting in a large amount of lift with lesser stress. All four camshafts are driven by a toothed belt with a self-adjusting belt tensioner. The belt assembly also includes two eccentric pulleys for timing adjustment.
The camshafts are direct-acting on the valves via hydraulic lifters. The hydraulic lifters adjust automatically to the change in length of the valves at different temperatures. They operate in an oil bath and are supplied with oil via an oil gallery in the cylinder head. The advantages of hydraulic lifters are their quiet operation and their reliability. In addition, each cylinder head has two air purging nozzles to eliminate tappet noise after starting.
The valves have chromium-plated stems and the exhaust valves are sodium filled for heat dissipation. The camshaft sprockets on the rear cylinder head are interchangeable as are the camshaft sprockets on the front cylinder head. The valve guides are pressed in the cylinder head and are not replaceable. They are serviced by reaming the guide to over-size diameter and installing valves with over-size valve stems.