Two compression rings and one oil slimming are installed on the piston.

Compression rings are designed to prevent gases breaking into a crankcase when compressing and expansion. In addition, they serve to transfer heat from the piston to the cylinder.

The oil slimming ring serves to remove the excess oil from the working surface of the cylinder and prevent it from entering the combustion chamber.

Замена шатунно-поршневой группы дизеля 740 КамазЗамена шатунно-поршневой группы дизеля 740 Камаз

We turn out four bolts of fastening heads, (Fig. 1) and remove the heads of the cylinder block.

I unscrew the nuts of the oil pan on the 13, remove the engine pallet and the pallet laying. In the case of a "biptic" of the crankcase, you need to knock on it through a wooden gasket.

Замена шатунно-поршневой группы дизеля 740 Камаз

Using keys to 13 and 17, remove the oil pump.

Замена шатунно-поршневой группы дизеля 740 Камаз

Remove the nuts of connecting rod bolts and remove the connecting rod lids (Fig. 4).

Since the lid sits tightly, to knock her down with rampant hammer blows. Remove the split bearing insert from the lid.

Замена шатунно-поршневой группы дизеля 740 Камаз

Press the piston in the cylinder so that it leaves the cylinder, and then take it out with the connecting rod.

We take out the connecting rod bearing from the rod.

Remove the piston with a connecting rod from the cylinder is careful not to damage the cylinder mirror.

Замена шатунно-поршневой группы дизеля 740 КамазЗамена шатунно-поршневой группы дизеля 740 Камаз

Check the tags on the connecting rod and the rod cover. If the labels are not visible - mark the connecting rod and the lid with the cylinder number.

In the same way, we take out the rest of the pistons with connecting rods.

Замена шатунно-поршневой группы дизеля 740 КамазЗамена шатунно-поршневой группы дизеля 740 Камаз

Using a plunger expander, remove the piston rings.

Remove the lock rings on both sides of the piston.

Heat the piston in the oil bath and remove the piston finger from the rod, before that, noticing the position of the connecting rod relative to the piston.

Замена шатунно-поршневой группы дизеля 740 Камаз

In the same way, remove the rest of the pistons from the connectors.

After disassembly, rinse all the details in gasoline. Clear pistons from Nagara. Clean the grooves under the piston rings with an old piston ring or a ring wreck.

Замена шатунно-поршневой группы дизеля 740 Камаз

To reduce nadporshnevogo clearance during engine assembly selection execution variant of the piston provide sealing action over its sleeve end by 0.5-0.7 mm.

embodiment Index piston (10, 20, 30, 40) supported on its bottom and on the inoperative end protrusion sleeves.

The diameter of the piston ring in the free state larger than the diameter of the cylinder, so if setting it tightly pressed against its walls.

The piston ring groove forms a labyrinth seal with a small gap.

The gases entering into the maze of nadporshnevogo space, reduce its pressure and velocity, and the ring is pressed against the cylinder wall.

A cut in the ring is called the castle. In operation, the ring must always be a gap in the castle, so that it is not jammed when heated.

The value of the gap during the installation of the piston into the cylinder is in the range 0.4-0.8 mm for compression rings, 0.3-0.7 mm for the oil scraper.

To ring free of springs, in their grooves on the piston height is also set with a small gap. Allen gap at the top compression ring is somewhat larger than the bottom.

Compression rings have a trapezoidal cross section.

The working surface of the upper compression ring is covered with chromium, has a mirror surface, the lower - molybdenum, it is matt.

During movement of the piston rings are pressed to the top, to the bottom plane of the grooves and create this desired seal against gas breakthrough into the crankcase through the grooves.

In this compression rings can pump oil into the combustion chamber being recorded by them with the cylinder wall when the piston moves downward, the oil is collected in the gap between the ring and the bottom plane of the groove and when moving upwards, oil is forced into the gap between the ring groove and the upper plane.

The vacuum in the cylinder during the intake stroke also contributes to this.

With an increase in the mechanical clearance in conjunction ring - the amount of oil being pumped into the combustion chamber recess of the piston due to the pumping action of the rings is increased, resulting in dramatically increases its consumption. It is therefore necessary to check the socket gap after installation of rings on the piston.

Scraper ring prefabricated; it consists of cast iron rings box section with chrome worktop and the coiled spring expander. rings chrome plating increases their durability.

Lower groove in the piston under the scraper ring has holes over the entire circumference for discharging oil, removes the ring from the cylinder surface.

The piston rod is connected with the floating type hollow finger, the axial displacement of which piston is limited by two snap rings.

Steel connecting rods, I-section. The big end detachable.

For accurate landing big end bearings finally treated with a cap assembly, whereby the cover rods are not interchangeable.

On the cover and a rod coated labels paired in the form of a three-digit sequence of numbers. In addition, the rod cover engraved serial number of the cylinder.

Sliding bearings in the upper head of the connecting rod are bimetallic unsplit bronze sleeve a working layer; the bottom head of a rod - removable interchangeable inserts.

Cover lower crosshead is fastened on two bolts nuts pressed into the lateral protrusions of the bottom head crank

Special locking rod bolts and nuts from samootvorachivaniya not provided.

This is due to the fact that the connecting rod bolts are automatically prevented from samootvorachivaniya due to friction in the thread is subject to strict performance requirements for tightening the screws connecting rod bolts.

Connecting rod bolts can rupture due to insufficient or excessive tightening. The bolts should be tightened to an elongation of 0,25 - 0,27mm.

Setting rings, pistons and liners in diesel 740 Kamaz

Замена шатунно-поршневой группы дизеля 740 Камаз

Installation of cylinder sleeves in the block

Before installing the sleeves in the block on the chamfer, lubricant cyatims is applied. Cylinder sleeves are inserted with an effort of hands carefully, not allowing the cutting of the spokes from the grooves of the sealing rings.

The piston with a finger and the connecting rod is assembled after heating the piston to a temperature of 80 ÷ 100˚ C.

Holes in the connecting rod under the finger and the finger itself is pre-lubricated with diesel oil.

The finger is established by the thumb strengthem. Pressing the finger is not allowed using the tool.

Замена шатунно-поршневой группы дизеля 740 Камаз

Molders on the piston and the grooves under the mustache must be located in one direction (Fig. 16). Piston fingers are fixed by locking rings.

Замена шатунно-поршневой группы дизеля 740 Камаз

The piston selection is made from the distance from the generator of the crankshaft crankshaft in the upper position to the stubborn cervic of the sleeve so that the bottom of the piston bottom over the stubborn boom of the cylinder liner was in the range of 0.6 ÷ 0.7 mm, Figure 17.

Замена шатунно-поршневой группы дизеля 740 Камаз

The method of measurement of the distance from the generator of the crankshaft forming the cranium neck in the upper position to the sealing coil of the cylinder liner is shown in Figure 18.

The data for the selection of the piston by the sleeve in Table 1.

Piston Index

Distance from forming

rod cervical

Before stubborn Burta

Cylinder sleeves, mm

Distance OT

Plane connector

to the center of the ring, mm


260,12 – 260,24

75,67 – 75,71


260,24 – 260,35

75,78 – 75,82


260,35 – 260,46

75,89 – 75,93


260,46 – 260,57

76,00 – 76 – 76,04

After selecting the pistons at the factory, the indexes of the piston options 10, 20, 30, 40 are applied on the bottom of the piston and on the non-working protrusion of the shelves.

When assembling, you need to pick up pistons and cylinders with the same index.

When installing the piston in the slide slide under the valves on the piston must be installed closer to the axis of the crankshaft.

The total gap between the ends of the lower heads of rods and crankshafts (axial backlash) should be at least 15 mm.

Piston rings before installing on the piston must have thermal gaps. The gap of the piston rings is measured in the caliber diameter of 120 + 0.03 mm.

Замена шатунно-поршневой группы дизеля 740 Камаз

The dimensions of the gaps are specified in the table.


Clearance after




Castle in compression rings

0,4 – 0,6


Castle in oilmaging piston rings

0,30 – 0,45


Top Clearance of the Upper Compression Ring

0,12  - 0,17


Torch gap of the lower compression ring

0,09 – 0,14


Oktsky gap of the oilmaging ring

0,07 – 0,11


Clearance in pairing piston - sleeve

(when measuring 0.119 - 1,162 mm from the bottom of the piston)

0,12 – 0,16


Install the piston rings using the plunger expander (if any).

The oil slimming ring is inserted into the piston groove and the ring is worn so that the extender's joint is at an angle of 180˚ to the ring of the ring.

After that, we install compression rings. First we insert a ring coated with molybdenum, after a ring covered with chrome. The castles of adjacent rings are bred in different directions.