The individual parts of the valve train, and above all the valve stems, stretch and elongate as the engine heats up. Therefore, for the normal operation of the valves, a small gap is required between the camshaft and the valve lifter (F-engine) and, accordingly, between the camshaft and rocker arm (C-engine). In order for you to understand the great importance of this type of engine adjustment, we will give a list of malfunctions that can occur if the clearance in the valve mechanism is incorrectly set:
— too little clearance causes the valves to not fit snugly against the seats, and this is especially true for very hot exhaust valves. However, they cannot give their heat to the seat rings. The edges of the valve heads are deformed, destroyed and the valve seats burn through. Compression decreases, the engine loses power, starts worse and consumes more fuel.
— too much gap in the valve train causes the valves to open later than necessary, the cylinders are not completely filled with mixture and the engine does not run at full power. The valve train, especially on C-engines, runs louder and wears out somewhat faster.