The crankshaft is made of high-quality steel and has five main and four connecting rod journals connected by cheeks and mated with transitional fillets

Kamaz-740.30-260 diesel crankshaftKamaz-740.30-260 diesel connecting rod

The crankshaft journals are angled at 90° for even stroke alternation.

Two connecting rods are attached to each crankpin (picture 2):

- one for the right and one for the left rows of cylinders.

The crankshaft is hardened by nitriding to a depth of 0.5-0.7 mm, the hardness of the hardened layer is at least 600 HV.

Oil is supplied to the connecting rod journals through holes in the main journals 8 and holes 7 (Figure 1) that do not intersect with lightening holes 6 in the connecting rod journals.

To balance the forces of inertia and reduce vibrations, the crankshaft has six counterweights stamped integrally with the cheeks of the crankshaft.

In addition to the main counterweights, there is an additional removable counterweight 1 pressed onto the shaft, its angular location relative to the crankshaft is determined by the key 5.

KAMAZ-740.30-260 diesel flywheelInstalling stop rings and liners

To ensure the required unbalance, sampling 6 is performed on the flywheel (Figure 3)

A neck 9 is made on the crankshaft shank (Figure 4), along which the crankshaft gear 8 and flywheel 1 are centered (Figure 5).


At the rear end of the crankshaft, ten threaded holes M16x1.5-6H are made for mounting the crankshaft gear and flywheel, and eight threaded holes M 12x1.25-6H are made at the front end for mounting the torsional vibration damper.

A plug 4 (Figure 1) is installed in the cavity of the toe of the crankshaft, through the calibrated hole of which the splined shaft of the front power take-off drive is lubricated.

The crankshaft is fixed against axial movements by two half rings 1 and two half rings 2 (Figure 4) installed in the grooves of the rear main bearing of the cylinder block, so that the grooved side is adjacent to the thrust ends of the shaft.

On the toe and shank of the crankshaft (Figure 1) there are gears for driving oil pumps 3, 2 and a gas distribution mechanism drive 8 (Figure 4).

The crankshaft is sealed with a rubber collar 8 (Figure 5), with an additional sealing element - boot 9.

The seal is located in the flywheel housing 4.

The collar is made of fluoroelastomer using the technology of molding the working sealing lip directly in the mold.

Nominal diameters of crankshaft journals:

  • - indigenous 95 -0.015 mm,
  • - connecting rod 80-0.013 mm.

Eight repair sizes of liners are provided for engine restoration.

The designation of the crankshaft bearing shells, the diameter of the crankshaft main journal, the diameter of the hole in the cylinder block for these shells are indicated in table 1

table of main liners

The designation of the liners of the lower head of the connecting rod, the diameter of the connecting rod neck of the crankshaft, the diameter of the hole in the crank head of the connecting rod for these liners are indicated in table 2

conrod bearing table

Inserts 7405.1005170 P0, 7405.1005171 P0, 7405.1005058 P0 are used when restoring the engine without grinding the crankshaft. If necessary, polish the crankshaft journals.

When grinding the crankshaft on the main journals of 94 mm or less or on the connecting rod journals of 79 mm or less, the crankshaft must be renitrided.

The tolerance limits for the diameter of the crankshaft journal, the diameter of the hole in the cylinder block and the diameter of the hole in the crank head of the connecting rod when rebuilding the engine must be the same as the nominal dimensions.

Engine crankshaft mod. 740.30-260 has the following main differences from the crankshafts of mod. 740.10 and 7403.10:

  • -hardening is done by nitriding instead of high frequency hardening;
  • - dirt trapping cavities in the connecting rod journals are excluded, oil is supplied to the connecting rod journals from the holes in the main journals with straight holes that do not intersect with the lightening holes in the connecting rod journals;
  • - a neck is made on the shank, along which the crankshaft gear and flywheel are centered.

These differences make it impossible to use the crankshafts of mod. 740.10 and 7403.10 for motors mod. 740.30-260.

The main and connecting rod bearings (figures 2 and 4) are made of steel tape coated with a layer of lead bronze 0.3 mm thick, with a layer of lead-tin alloy 0.022 mm thick. and a layer of tin 0.003 mm thick.

Top 3 and bottom 4 main bearing shells are not interchangeable.

The top liner has a hole for oil supply and a groove for its distribution.

Both bearings of the 4th connecting rod are interchangeable.

From rotation and lateral displacement, the liners are fixed with protrusions (mustache) included in the grooves provided in the beds of the block and connecting rod, as well as bearing caps.

The liners have design differences aimed at improving their performance when forcing the engine with a turbocharger, while the marking of the liners has been changed to 7405.1004058 (connecting rod), 7405.1005170 and 7405.1005171 (main).

It is not recommended to replace liners during repair with serial bearings marked 740, as this will significantly reduce the engine life.


The main bearing caps (picture 8) are made of ductile iron.

The covers are fastened with the help of vertical and horizontal coupling bolts 3, 4, 5, which are tightened according to a certain pattern with a regulated moment (article - Tightening torques for KAMAZ diesel connections).

Connecting rod (picture 2) steel, forged, rod 1 has an I-section.

The upper head of the connecting rod is one-piece, the lower one is made with a straight and flat connector. The connecting rod is finished assembled with a cap 2, so the caps of the connecting rods are not interchangeable.

A steel-bronze bushing 3 is pressed into the upper head of the connecting rod, and replaceable liners 4 are installed into the lower head.

The cover of the lower head of the connecting rod is fastened with nuts 6, screwed onto bolts 5, pre-pressed into the rod of the connecting rod.

The connecting rod bolts are tightened according to the scheme defined in the article KAMAZ diesel engine tightening torques.< /p>

The cap and connecting rod are marked with mating marks - three-digit serial numbers. In addition, the serial number of the cylinder is stamped on the connecting rod cap.

Flywheel (Figure 3) is fixed with ten bolts 7 (Figure 5), made of alloy steel, on the rear end of the crankshaft and fixed with a pin 10 (Figure 5) on the centering journal of the crankshaft 9 (Figure 4).

In order to prevent damage to the flywheel surface, a washer 6 is installed under the bolt heads (Figure 5).

The value of the tightening torque of the flywheel mounting bolts is indicated in the article - Tightening torques for KAMAZ diesel connections.

A toothed rim 3 (Figure 3) is pressed onto the machined cylindrical surface of the flywheel, with which the starter gear engages when starting the engine.

A ring 1 with an outer chrome-plated surface is installed under the crankshaft seal collar.

The flywheel is made for one or two disc diaphragm clutches. Bearing 5 of the input shaft of the gearbox is installed in the inner bore of the flywheel.

Kamaz flywheel lock

When adjusting the fuel injection advance angle and thermal clearances in the valves, the flywheel is fixed with a retainer (Figure 9).

The design of the flywheel has the following main differences from the flywheels of the 740.10 and 7403.10 engines:

  • - the angle of the slot for the latch on the outer surface of the flywheel has been changed;
  • - the diameter of the bore has been increased to accommodate the washer for the flywheel mounting bolts;
  • - crescent sampling introduced to provide the required imbalance;
  • - the flywheel is fastened to the end of the crankshaft by ten bolts M16x1.5;

The above changes make it impossible to install the flywheels of engines 740.10 and 7403.10 during repair work.

Kamaz crankshaft torsional vibration damperKamaz crankshaft vibration damper mounting

The vibration damper (Figure 10) is fixed with eight bolts 2 (Figure 11) on the front toe of the crankshaft.

The absorber consists of a housing 1 (Figure 10) in which the absorber flywheel 2 is installed with a gap.

Outside, the damper body is closed with cover 3.

Tightness is ensured by welding at the junction of the absorber body and cover.

There is a high-viscosity silicone fluid between the damper body and the damper flywheel, which is dosed before the cover is sealed.

The absorber is centered using washer 6 welded to the body.

The damping of torsional vibrations of the crankshaft occurs by braking the damper housing, mounted on the toe of the crankshaft, relative to the flywheel in a silicone fluid environment. In this case, the braking energy is released in the form of heat.

It is STRICTLY FORBIDDEN to deform the body and cover of the absorber during repair work.

An absorber with a deformed body or cover is not suitable for further use.

After installing the damper, check for clearance between the damper and counterweight.

Kamaz diesel piston

Piston 1 (picture 12) is cast from aluminum alloy with a wear-resistant cast iron insert under the upper compression ring.

The piston head has a toroidal combustion chamber with a displacer in the central part, which is offset relative to the piston axis by 5 mm away from the grooves for the valves.

The side surface is a complex oval-barrel-shaped shape with an underestimation in the area of ​​the holes for the piston pin. The skirt is coated with graphite.

A groove is made in its lower part, which, if properly assembled, prevents the piston from contacting the cooling nozzle when it is at bottom dead center.

The piston is equipped with two compression and one oil scraper rings.

Its distinctive feature is the reduced distance from the bottom to the lower end of the upper groove, which is 17 mm.

On the 740.30-260 engine, similarly to other models of KAMAZ engines, in order to ensure fuel efficiency and environmental performance, a selective selection of pistons for each cylinder is used for the distance from the axis of the piston pin to the bottom.

According to the specified parameter, the pistons are divided into four groups 10, 20, 30 and 40. Each subsequent group differs from the previous one by 0.11 mm.

Pistons of the greatest height are supplied as spare parts, therefore, in order to avoid possible contact between them and the cylinder heads, in case of replacement, it is necessary to control the over-piston clearance.

If the gap between the piston and the cylinder head after tightening the bolts of its fastening is less than 0.87 mm, it is necessary to cut the piston head by the amount missing from this value.

Installation of pistons from KAMAZ engines of other models is not allowed

Compression rings (picture 12) are made of high-strength cast iron, and the oil scraper is made of gray cast iron.

The upper compression ring has the shape of a double-sided trapezoid, with an internal recess from the side of the upper end, and the second has the shape of a one-sided trapezoid.

When mounting, the end marked "top" must be located on the side of the piston head.

The working surface of the upper compression ring 4 is covered with molybdenum and has a barrel shape.

Chromium is applied to the working surface of the second compression 5 and oil scraper rings 2.

Its shape on the second ring is a cone with a slope towards the lower end, for this characteristic feature the ring was called "minute".

Minute rings are used to reduce oil consumption for waste, their installation in the upper groove is unacceptable.

Box-type oil scraper ring, 4 mm high, with a spring expander having a variable pitch of turns and a ground outer surface.

The middle part of the expander with a smaller pitch of turns, when installed on the piston, should be located in the lock of the ring.

Installing piston rings from other models of KAMAZ engines can lead to an increase in oil consumption for waste.

sleeve with Kamaz diesel piston

Cooling nozzles (Figure 13) are installed in the crankcase of the cylinder block and provide oil supply from the main oil line, when it reaches a pressure of 80-120 kPa (0.8-1.2 kg / see2), on the inner cavity of the pistons.

The valve located in each of the nozzles is adjusted to this pressure.

When assembling the engine, it is necessary to control the correct position of the nozzle tube relative to the cylinder liner and piston. Contact with the piston is not allowed.

The piston with the connecting rod (Figure 12) are connected by pin 3 of a floating type, its axial movement is limited by retaining rings 6.

The pin is made of chromium-nickel steel, hole diameter 22 mm. The use of pins with a hole of 25 mm is unacceptable, as this disturbs the balance of the engine.

Front PTO and Pulley Drive

Front power take-off drive (Figure 14) is carried out from the crankshaft nose through the power take-off half coupling 2 attached to the crankshaft nose 13 with eight special bolts M l2x1.25.

The centering of the coupling half relative to the crankshaft is carried out along the internal bore of the external counterweight.

The torque from the coupling half is transmitted through the drive shaft of the units 1 and the power take-off shaft 3 to the pulley 4.

The power take-off shaft 3 is mounted on two ball bearings 11 and 12. The cavity is sealed with a cuff 8.

To reduce the wear of the spline joints, the drive shaft of the units is kept from axial movement by the spring 9.