Steel camshaft with hardened cams and distributor drive gear, driven by two gears

The camshaft rests on five bearings equipped with bimetallic tape bushings, the diametrical clearances in the camshaft bearings in the new engine are within 0.03-0.09 mm for the four front bearings and within 0.025-0.077 mm for the fifth rear bearing.

The axial movement of the camshaft is limited by a flange located between the gear and the front end of the first neck, which is attached to the front end of the block with two bolts.

The difference between the height of the spacer ring, put on the front camshaft trunnion, and the thickness of the flange is 0.08-0.208 mm.

These values ​​correspond to the axial clearance at the camshaft of a new engine.

Position of the marks on the gears when setting the gas distribution

For the correct mutual installation of the gears, you need to put the crankshaft gear and the camshaft gear so that the marks are on the same straight line connecting the centers of these gears (Fig. 1).

Valves - upper, located in the cylinder head in one row, obliquely to the cylinder axis; are driven from the camshaft using rods, pushers and rocker arms.

The valves are made of heat-resistant steel; - angle of the working chamfer of the inlet valve seat 30°, outlet 45°; the exhaust valve stem has a sodium-filled hole, and the poppet has a heat-resistant surfacing of the seating chamfer.

Exhaust valves are forcibly rotated during engine operation by a special mechanism to increase their service life.

Exhaust valve and its rotation mechanism

The exhaust valve rotation mechanism (Fig. 2) consists of a fixed body 2, five balls 3 and their return springs 10 (located in inclined recesses of the body, made in an arc), a disk spring 9, a thrust washer 4, which is pressed by the valve spring through lock ring 5.

The thrust washer 4 and the disc spring with a gap are put on the protrusion of the housing, which is located in a special socket of the block head (Fig. 3).

Exhaust valve rotation diagram

When the valve is closed (Fig. 3, a), the force of the spring 6 is transmitted through the thrust washer 4 to the outer edge of the disc spring 9, which rests with its inner edge against the body shoulder 2.

During the opening of the valve (Fig. 3, b), the force of the valve spring increases; under the influence of increased force, the disc spring, leaning on the balls, straightens;

- a gap appears between the inner edge of the spring and the body shoulder, and the force of the springs 10 begins to be transferred to the balls 3, which, rolling over the inclined surfaces of the recesses, turn the disk spring 9 and the thrust washer 4 at some angle, and with them the valve spring 6 and valve 1.

During the closing of the valve (Fig. 3, c), the force of the valve spring decreases, the deflection of the disc spring increases; it rests against the shoulder of the body, releasing the balls, which, under the action of the springs, return to their original position, wedging between the washer and the inclined surface of the body.

At any disassembly of an engine that has traveled more than 70,000 km, it is necessary to check the condition of the springs 10 (see Fig. 2 and 3) and the balls of the exhaust valve rotation mechanism.

If traces of wear are found on the coils of the spring, it is necessary to turn the spring with the worked out section down.

When assembling the valve rotation mechanism, pay attention to the correct installation of balls and springs.

When properly assembled, the springs should be located behind the balls relative to the chosen direction of rotation.

Valve rockers forged, steel, with bronze bushing.

Valve tappets steel, hollow. to increase the reliability of the cam-pusher pair, special cast iron is deposited on the end of the pusher.

At the bottom of the tappet there are holes for draining the oil that enters the tappet.

Steel rods with hardened spherical ends.

Inlet gas pipeline made of aluminum alloy, common to both rows of cylinders, located between the heads of the block and equipped with a water jacket for heating the mixture.

The tightening of the nuts securing the intake gas pipeline to the cylinder head must be done evenly, adhering to the tightening crosswise from the middle to the edges of the gas pipeline, so that the rubber gasket does not extrude from the joint between the intake pipe and the head.

Nut torque up toshould be within 2-2.5 kGm.

Exhaust pipes made of ductile iron, one on each side of the unit.

The assembly of the composite gas pipeline on the engine must be carried out in the following order:

  • - the joint of the gasket must be located under the clamp bolt; the axis of the bolt tightening the clamp on the short arm of the gas pipeline must be perpendicular to the flanges of the gas pipeline to the cylinder head;
  • - the axis of the bolt tightening the clamp on the long arm of the gas pipeline must be parallel to the flanges of the gas pipeline to the cylinder head.

The bolt is installed with the head up; bolt tightening torque 1.4-1.7 kgm.

Tighten the nuts for fastening the composite exhaust gas pipeline to the cylinder head in the following sequence: middle flange - first fasten the lower nut, then the upper one, tightening torque 4-4.5 kgm; extreme flanges - fasten the nuts with a tightening torque of 3-3.5 kgm.