Main dimensions of valves and guide bushings
The cylinder head is common to all four cylinders and is cast from an aluminum alloy. The main dimensions of the cylinder head, valves, and guide bushings are shown in the figure.
Cast iron valve seats and valve guides are pressed into the cylinder head. The working chamfers of the seats are machined after pressing in assembly with the cylinder head to ensure precise alignment of the chamfers with the holes in the valve guides.
The holes in the bushings are also machined after pressing the bushings into the cylinder head. This is done to ensure the accuracy of the hole diameter and its location relative to the working chamfers of the seat and valve. The holes in the guide bushings have spiral grooves for lubrication. The inlet valve bushings have grooves cut to half the length of the hole, and the exhaust valve bushings have grooves cut along the entire length of the hole.
Oil-deflecting caps made of heat- and oil-resistant rubber with a steel reinforcement ring are placed on top of the guide bushings. The caps cover the valve stems and serve to reduce the penetration of oil into the combustion chamber through the gaps between the guide bushing and the valve stem.
Each valve has two cylindrical springs: external and internal, resting on two support washers. At the top, the springs rest against a plate, which is held on the valve stem by two crackers, which have the shape of a truncated cone when folded.