Clean the piston heads and piston ring grooves from carbon deposits.
Pistons in the cylinders of the block must be installed group by group, in accordance with the table.
Pistons according to the outer diameter of the skirt and cylinders according to the internal diameter are sorted into three size groups and marked with the letters - A, B, C.
A letter indicating the size group of the cylinder diameter is painted on the outer surface of the cylinder block on the right, opposite each cylinder.
Size groups of cylinder diameters are determined during the manufacture of the cylinder block.
When repairing a used engine with worn cylinders, it is necessary to re-measure the cylinder diameters and determine their group.
Cylinder diameters should be measured at a temperature of 20±3°C.
Pistons are marked with letters on the bottom (Fig. 1).
The largest diameter of the piston skirt is located in a plane perpendicular to the piston pin axis at a distance of 47.5 mm from the piston bottom.
Measure the piston skirt diameters at a piston temperature of 20 ± 3 °C.
Pins by outer diameter, connecting rods and pistons by pin hole diameter are sorted into four size groups, which are marked with paint or Roman numerals (Table 1).
The size group of the connecting rod hole for the pin is marked with paint on the rod in the area of the piston head.
The piston hole group is designated by Roman numerals stamped on its bottom (Fig. 1), and the pin by Roman numerals stamped on the end.
The connecting rod must be assembled with a pin of the same size group.
If the non-parallelism of the axes of the holes of the piston and crank heads exceeds the maximum permissible value, the connecting rod is deformed and must be replaced.
If the hole in the connecting rod bushing for the pin is worn beyond the acceptable level, it is necessary to replace the bushing, make a groove in the bushing for the oil channel and machine the hole in the bushing for the pin.
Before installing a new bushing, measure the diameter of the connecting rod mounting hole - if the hole wear exceeds the acceptable limit, the connecting rod should be rejected.
Measure pistons, pins and connecting rods at a temperature of 20±3 °C.
Connecting rods are sorted into three groups by weight and marked with paint on the connecting rod cover (Fig. 1). Marking color:
- white - corresponds to the mass of the connecting rod 900-905 g;
- green - 895-900 g;
- yellow - 890-895 g.
Size groups of pistons and cylinders of the block
Group A:
- piston diameter (skirt) - 95.488 - 95.500 mm;
- cylinder diameter - 95.536 - 95.548 mm.
Group B:
- piston diameter (skirt) - 95.500 - 95.512 mm;
- cylinder diameter - 95.548 - 95.560 mm.
Group C:
- piston diameter (skirt) - 95.512 - 95.524 mm;
- cylinder diameter - 95.560 - 95.572 mm.
Group AI repair increase 0.25:
- piston diameter (skirt) - 95.738 - 95.750 mm;
- cylinder diameter - 95.786 - 95.798 mm.
Group BI repair increase 0.25:
- piston diameter (skirt) - 95.750 - 95.762 mm;
- cylinder diameter - 95.798 - 95.810 mm.
Group CI repair increase 0.25:
- piston diameter (skirt) - 95.762 - 95.774 mm;
- cylinder diameter - 95.810 - 95.822 mm.
Group AII repair increase 0.5:
- piston diameter (skirt) - 95.988 - 96.000 mm;
- cylinder diameter - 96.036 - 96.048 mm.
Group BII repair increase 0.5:
- piston diameter (skirt) - 96.000 - 96.012 mm;
- cylinder diameter - 96.048 - 96.060 mm.
Group CII repair increase 0.5:
- piston diameter (skirt) - 96.012 - 96.024 mm;
- cylinder diameter - 96.060 - 96.072 mm.
Size groups of pins, pistons and connecting rods
Pin diameter - 21.9935—21.9960 mm:
- holes in the piston boss - 21.9975—22.0000 mm;
- holes in the connecting rod bushing - 22.0045—22.0070 mm;
- connecting rod marking - white;
- piston and pin marking - "I".
Pin diameter - 21.9910—21.9935 mm:
- holes in the piston boss - 21.9950—21.9975 mm;
- holes in the connecting rod bushing - 22.0020—22.0045 mm;
- connecting rod marking - green;
- piston and pin marking - "II".
Pin diameter - 21.9885—21.9910 mm:
- holes in the piston boss - 21.9925—21.9950 mm;
- holes in the connecting rod bushing - 21.9995—22.0020 mm;
- connecting rod marking - yellow;
- piston and pin marking - "III".
Pin diameter - 21.9860—21.9885 mm:
- holes in the piston boss - 21.9900—21.9925 mm;
- holes in the connecting rod bushing - 21.9970—21.9995 mm;
- connecting rod marking - red;
- piston and pin marking - "IV".
For installation on the engine, you should take connecting rods of the same weight group.
Pistons are not sorted by weight.
Check the difference in mass of the selected sets of piston, pin, connecting rod and rings, which should not exceed 10 g.
If there is a greater difference in the masses of the sets, in order to eliminate increased engine vibrations, the mass of the sets should be equalized. To do this, remove metal from the connecting rods of heavier sets from the weight bosses of the piston or crank heads, depending on the mass of the heads, to a size not less than that shown in Fig. 2.
When removing material, the mass of the connecting rod heads should not exceed the following limits: piston head (m 1) - 211-217 g, crank head (m 2) - 679-688 g.
Lubricate the piston pin with engine oil and insert it into the holes of the piston and connecting rod.
Connecting rods and pistons, when assembled with a piston pin, must be oriented as follows: the inscription "FRONT" located on the outside of the pin boss and the protrusion "A" on the crank head of the connecting rod must be directed in the same direction.
The connecting rod cover on the connecting rod must be installed so that the ledge "B" on the connecting rod cover and the ledge "A" on the crank head or the cylinder numbers stamped on the side surface of the cover and crank head or the grooves for the bearings are located on one side (Fig. 1).
Rings intended for installation in cylinders of nominal diameter are marked with yellow paint on the upper compression ring.
For installation in cylinders of the first repair size - blue, of the second repair size - green.
The end gap, measured at the joints placed in the cylinder (Fig. 4), for new rings should be:
- 0.25-0.45 mm for the upper compression ring;
- 0.45-0.65 mm for the lower compression ring;
- 0.30-0.55 mm for the box-type oil scraper ring.
For worn rings, the maximum allowable end gap is no more than 1.5 mm.
Place rings for measuring the end gap in the upper unworn part of the cylinder (from the upper edge of the cylinder to the location of the first compression ring when the piston is at TDC) or in a mandrel of the same diameter.
Pre-clean the surface of the cylinder from carbon deposits.
Installing piston rings with a smaller end gap at the joint will lead to the ring ends touching during engine operation and cylinder scoring.
Installing worn rings with a large gap will lead to a decrease in compression pressure and increased oil consumption.
Check the side clearance between the rings and the piston groove wall with a feeler gauge (Fig. 5). Check around the circumference of the piston at several points.
The side clearance should be 0.045-0.090 mm for new rings and pistons. For worn rings and pistons, a maximum clearance of no more than 0.15 mm is allowed.
A larger gap will lead to increased oil consumption due to the "pumping" action of the rings.
Place the piston rings onto the piston using the tool (Fig. 6).
Install the lower compression ring with the inscription "TOP" on the end facing the piston crown. The rings in the grooves must move freely.
Insert the pistons into the cylinders as follows:
- orient the connecting rod-piston assembly so that the inscription "FRONT" on the piston boss faces the front of the cylinder block;
- wipe the connecting rod bearing bores and their caps with a cloth, wipe and insert the bearing shells;
- turn the crankshaft so that the crankpins of the first and fourth cylinders are at BDC;
- lubricate the bearing shells, piston, connecting rod journal and first cylinder with clean engine oil;
- space the ring gaps at approximately 120° to each other. The expander spring joint should be placed opposite the oil scraper ring gap before installing the ring on the piston.
It is recommended not to position the ring gaps in a plane perpendicular to the pin axis.
Install protective caps on the connecting rod bolts. Using a special ring compressor with an internal conical surface, compress the rings and insert the piston into the cylinder (Fig. 7).
Before installing the piston, once again make sure that the numbers stamped on the connecting rod and its cap correspond to the cylinder number, and check the correct orientation of the piston and connecting rod in the cylinder.
Pull the connecting rod by the crank head onto the connecting rod journal, remove the protective caps from the bolts, and install the connecting rod cap.
The connecting rod cap should be installed so that the numbers stamped on the cap and connecting rod, or the grooves for the bearing shells, are on the same side.
Tighten the nuts with a torque wrench to 68-75 N⋅m (6.8-7.5 kgf⋅m).
Insert the piston of the fourth cylinder in the same manner.
Rotate the crankshaft 180° and insert the pistons of the second and third cylinders.
Rotate the crankshaft several times. It should rotate easily with little effort.
