The camshaft usually operates the valves directly via a bucket tappet. The intake valve opening mechanism incorporates a valve tappet and a piston inside a chamber. Tappet adjustment was by eccentric rocker shaft. Light alloy is used for the valve covers, tappet blocks, sump and inlet manifolds. With a short-stroke or tappet system, the piston moves separately from the bolt group. Another reason is the large tappet clearance on the exhaust valve. I, despite the new engine's hydraulic tappet operation. The tappet clearances are maintained by the flow of the engine's lubricating oil. In this configuration, the rockers combined the function of sliding tappet, rocker and adjustment device. Vacuum pump located on tappet cover. This type of engine still has tappet noise even after adjustment. It operates in a similar manner to tappet locking except that the blades are curved. The remained signal boxes use 5-bar tappet locking frames dating from the 1930s.