Valve guide bushings are also made of cast iron and are pressed into the cylinder head with tension. On the outer surface of the guide bushings there is a groove into which a retaining ring is inserted. It ensures the accuracy of the bushing position when pressing them into the cylinder head and protects the bushings from possible falling out.
The holes in the bushings are machined after they are pressed into the cylinder head. This ensures a narrow tolerance on the diameter of the hole and the accuracy of 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 stem and serve to reduce oil penetration into the combustion chamber through the gaps between the guide bushing and the stem.
The valves are driven by a camshaft rotating in the bearing housing through intermediate levers. The clearance between the camshaft cams and the lever is set by an adjusting bolt, on the spherical head of which the lever swings. The bolt is held from self-loosening by a lock nut.
The valves have two cylindrical springs - external and internal, clamped between a plate (top) and two support washers (bottom). The spring plate is held on the valve stem by two crackers, which have the shape of a truncated cone when folded. Each lever is pressed against the end of the valve by a special (stud) spring.
To increase the wear resistance of the rod, both valves are nitrided, and the ends of the rods on which the levers rest are hardened with high-frequency current.
The camshaft is cast iron, identical for all engine models. It rests on 5 journals and rotates in an aluminum bearing housing mounted on the cylinder head. A driven sprocket is attached to the front end of the camshaft. The camshaft is held from axial movement by a thrust flange placed in the groove of the front support journal of the shaft.
The camshaft is driven by a double-row roller chain from the crankshaft drive sprocket. The same chain also drives the auxiliary drive shaft. The chain drive has a semi-automatic tensioner with a shoe and a chain damper with plastic pads. A limiting pin is installed at the bottom of the cylinder block to prevent the chain from falling into the crankcase when removing (by car) camshaft sprockets.
For the correct mutual arrangement of the sprockets, i.e. for setting the valve timing, there are upper and lower installation marks. The upper ones are located on the camshaft sprocket and bearing housing, the lower marks are on the crankshaft sprocket and camshaft drive cover.