The engine cylinder block is cast from cast iron.
The casting is subjected to artificial ageing to relieve thermal stresses, which allows the block to maintain correct geometric shapes and dimensions during operation.
Two rows of half-blocks for the cylinder liners, cast integrally with the upper part of the crankcase, are arranged at an angle of 90° to each other.
The left-hand row of the bores for the liners is offset relative to the right-hand one forward (towards the fan) by 29.5 mm, which is due to the installation of two connecting rods on each connecting rod journal of the crankshaft.
Each bore has two coaxial cylindrical holes, made in the upper and lower bands of the block, by which the cylinder liners are centred, and recesses in the upper band, forming annular seats for the collars of the liners.
To ensure correct seating of the liner in the block, the parameters of flatness and perpendicularity of the thrust seat under the liner collar relative to the axis of the centring bores are made with high precision.
On the lower band, two grooves for the sealing rings are made, which prevent the ingress of coolant from the cooling cavity of the block into the cavity of the engine oil sump.
The bosses of the holes for the cylinder head fastening bolts are made in the form of bosses on the transverse walls forming the cooling jacket, uniformly distributed around each cylinder.
The crankcase part of the block is connected to the main bearing caps by main and draw bolts.
The centring of the main bearing caps is carried out by horizontal pins 8 (Figure 1), which are pressed in at the joint between the block and the caps, but for the most part enter the block to prevent them from falling out when the caps are removed.
In addition, the fifth main support cap is centred in the longitudinal direction by two vertical pins, ensuring the accuracy of coincidence of the bores for the crankshaft thrust half-rings on the block and on the caps.
The order of tightening the fastening bolts of the main support caps is in accordance with the article — «Tightening torques of the diesel fasteners».
The boring of the cylinder block for the main bearing shells is carried out assembled with the caps, therefore the main bearing caps are not interchangeable and are installed in a strictly determined position.
On each cap, the ordinal number of the support is applied, the numbering of which starts from the front end face of the block.
In the crankcase part of the centre of the cylinder block, in the form of bosses, the guides of the valve tappets are made.
Closer to the rear end face, between the fourth and eighth cylinders, to improve the coolant circulation, a bypass pipe of the cooling cavity is made.
At the same time, it gives the block additional rigidity.
Parallel to the axis of the bores for the crankshaft bearings, bores for the camshaft bushes of increased dimension are made.
The diameters of the oil channels in the cylinder block are increased.
In the lower part of the cylinders, bosses for the piston cooling nozzles are cast integrally with the block.
In order to install the filter with the heat exchanger on the block, on the right-hand side, compared with the 740.10 engine, the platform under the filter has been increased, two additional fastening holes and a drain hole from the filter have been introduced.
The cylinder liners (Figure 2) are of the «wet» type, easily removable, and bear the marking 740.50-1002021 on the conical part at the bottom of the liner.
The installation of liners with a different marking is not permissible due to the contact that occurs with the connecting rod.
The liners of the 740.50-360 and 740.51-320 engines differ by a height 3 mm less than the liners of other KAMAZ engine models of 120×120 dimension.
The cylinder liner is made of special grey cast iron, hardened by volumetric quenching.
In the liner — cylinder block joint, the cooling cavity is sealed by circular-section rubber rings.
In the upper part, ring 5 is installed in the liner groove; in the lower part — two rings 4 in the bores of the cylinder block.
The microrelief on the liner mirror is a sparse network of depressions and platforms with small scratches at an angle to the liner axis.
During engine operation, the oil is retained in the depressions, which improves the running-in of the parts of the cylinder-piston group.
During engine assembly, on the non-working projection of the liner end face, the cylinder number and the index of the piston version are applied.
The unit drive (Figure 3) is carried out by straight-toothed gears and serves to drive the valve timing mechanism, the high-pressure fuel pump, the compressor and the vehicle power steering pump.
The valve timing mechanism is driven from the gear 10, installed on the crankshaft end, through the block of intermediate gears, which rotate on two rows of rollers 3, separated by the intermediate bush 4 and located on the axle 1, fastened on the rear end face of the cylinder block.
On the end of the camshaft, a gear is press-fitted, the angular position of which relative to the shaft cams is determined by the key.
The gear 15 of the high-pressure fuel pump (HPFP) drive is installed on the shaft 13 of the HPFP drive and is fixed by the key 14.
The gears are installed on the engine in a strictly determined position according to the mark «0» on the camshaft drive gear, the mark «E» on the HPFP drive gear and the scratches stamped on the gear wheels, as shown in Figure 3.
The HPFP drive is carried out from the gear 15, which is in engagement with the camshaft gear.
The rotation from the shaft to the HPFP is transmitted through the driving and driven half-couplings with elastic plates, which compensate for the misalignment of the installation of the HPFP shafts and the gear.
With the HPFP drive gear, the drive gears of the compressor and the power steering pump are in engagement.
To the rear end face of the cylinder block, the unit housing is fastened. In the upper part of the unit housing there are bores, into which the compressor and the power steering pump are installed.
On the sides of the unit housing, bosses with holes for oil drainage from the turbochargers and a hole for the oil level dipstick are made.
The unit drive is closed by the flywheel housing, fastened to the rear end face of the cylinder block through the unit housing.
On the flywheel housing on the right, a place is provided for installing the flywheel locking tool, used for setting the fuel injection advance angle and adjusting the thermal clearances in the valve timing mechanism.
The handle of the locking tool during engine operation must be in the upper position.
It is moved to the lower position during adjustment work; in this case, the locking tool is in engagement with the flywheel.
In the upper part of the flywheel housing, a bore is made, into which the rear bearing housing is installed.
At the bottom in the left part of the housing, there is a bore, into which the starter is installed. In the middle of the housing, a bore for the crankshaft oil seal is made.
In the upper part of the housing on the left, a boss is made, intended for installing the power take-off box (PTO). In the absence of the PTO, the inner surfaces of the boss are not machined.
The rear flange of the flywheel housing is made with connecting dimensions according to SAE1.
