Valve Train

Both camshafts are driven by a shared timing chain, and operate four valves per cylinder by means of an selective shim setting on the top of a tappet. One spring on each valve is used to close the valve. The adjusting shims in the valve tappets can be changed to correct the valve clearance. These are available in 44 different thicknesses. The shim thickness is ink printed on the back of the shim. Using a special procedure, the camshafts can be lifted without timing chain disassembly to change the shims. A high degree of accuracy is required during adjusting to avoid repeated changing of the shims. The camshaft cams run concentrically on the valve tappets. At engine speeds of about 3,000 rpm this causes the tappets to rotate, and they in turn transfer the rotation to the valves. This valve rotation is required because it produces an even valve seating and prevents the valves from wearing in a certain position which could cause them to leak.