The clearance between the oil scraper ring and the piston groove should be within the range of 0.135–0.335 mm.

The gaps in the piston ring locks should be in the range of 0.3–0.7 mm for compression rings and 0.3–1.0 mm for oil scraper rings.

Dimensional groups of pistons, connecting rods and pins are shown in the table at the end of the article.

Pins and connecting rods are marked with paint: the finger is in the hole, the connecting rod is on the rod near the upper head.

A Roman numeral is stamped on the piston crown showing the piston group.

The pin should not fall out of the connecting rod head when tilted at approximately 45 °.

The difference in weight between pistons assembled with connecting rods, pins, piston rings installed on one engine should be no more than 12 g.

Disassembly and inspection of the connecting rod-piston group

Remove the piston rings with a puller. If there is no puller, you can remove the rings by carefully unbending the rings at the locks.

Ремонт шатунно-поршневой группы ЗМЗ-402

Ремонт шатунно-поршневой группы ЗМЗ-402

Remove circlip from both sides of the piston

We knock out the piston pins with light hammer blows through the mandrel 1. Remove the connecting rod 2 from the piston 3

Remove the remaining pistons from the connecting rods in the same way.

1. Inspect the pistons. If they have seizures, traces of burnout, deep scratches, replace the pistons.

Measure the piston diameter. If it is less than 91.9 mm, replace the piston.

The piston diameter is measured in a plane perpendicular to the piston pin axis, 8.0 mm below the piston pin axis.

The piston is installed in the cylinder with a clearance of 0.024–0.048 mm.

In order to ensure the size of the clearance, the pistons are divided by diameter into five size groups A, B, C, D and D.

The lettering is knocked out on the piston crown.

When matching the piston to the cylinder, the above clearance must be ensured.

The maximum permissible clearance between the piston and the cylinder is 0.25 mm.

The clearance between the piston and the cylinder can be determined by measuring the piston and cylinder.

The spare parts are supplied with pistons of two overhaul sizes: with a diameter increased by 0.5 mm and by 1.0 mm.

2. Measure the piston ring-to-piston groove clearance at several locations around the circumference of the piston.

The clearance should be between 0.05–0.087 mm for compression rings and 0.115–0.365 mm for the oil scraper ring.

If the clearances exceed those specified, the rings or pistons must be replaced.

Замер зазора между поршневым кольцом и канавкой поршня

3. Measure the clearances in the piston ring locks. To do this, insert the ring into the cylinder and push it with the piston like a mandrel so that the ring fits in the cylinder evenly, without distortions.

Measure the gap in the ring lock with a feeler gauge; it should be in the range of 0.3–0.6 mm for compression rings and 0.5–1.0 mm for oil scraper disks.

Замер зазора в замках поршневых колец

If the clearance exceeds the specified, replace the ring. If the gap is less, you can saw off the ends of the ring with a file clamped in a vice. In this case, the ring is moved up and down the file.

4. Check the seating of the piston pin in the upper connecting rod head.

The gap between the pin and the bushing of the upper connecting rod head should be in the range of 0.0045-0.0095 mm.

Pins, pistons and connecting rods are divided into four size groups and are marked with paint.

The pin is marked on the inner surface at one end, the connecting rod - on the rod, the piston - on the lower surface of one of the lugs, or a Roman numeral is knocked out on the piston bottom.

Lightly lubricate the gudgeon pin with engine oil and insert into the upper connecting rod head.

The finger should enter the head from the effort of the thumb evenly, without jamming.

The connecting rod should rotate on the pin under its own weight from a horizontal position.

The pin should not protrude or fall out of the connecting rod head under its own weight if the connecting rod is rotated so that the pin is vertical.

Piston pin and connecting rod must be in the same or adjacent size groups.

5. Pistons with piston rings, pins and connecting rods are selected by weight.

The difference in weight for one engine should be no more than 12 g.

6. Inspect the connecting rod bushings. If they have seizures, risks, chipping, etc., they must be replaced.

7. Install the caps on the connecting rods and measure the diameter of the hole in the lower connecting rod head.

The nominal hole diameter is 60 +0.019 mm, the maximum permissible diameter is 60.03 mm.

If the measured diameter exceeds the maximum permissible, replace the connecting rod with a cap.

Measure the diameter of the hole in the bushing of the upper connecting rod. Nominal hole diameters 22 +0.007 and 22 –0.003 mm, maximum allowable - 22.01 mm.

If the measured diameter exceeds the limit, replace the connecting rod.

Assembly and installation of pistons with connecting rods

Сборка и установка поршней с шатунами

1. Assemble piston 4 with connecting rod 3. Before that, heat the piston to a temperature of 60–80 ° C.

Then quickly insert the connecting rod into the piston so that the inscription: "Front" on the piston and the protrusion A on the connecting rod are on one side, and press in the piston pin 6.

Install circlip 5.

Slide the piston rings onto the piston using a puller.

On the upper compression ring there is an inscription: "Top", the ring should be installed on the piston with this inscription to the bottom of the piston.

There is a groove on the lower compression ring on the inside, the ring must be installed with this groove up to the bottom of the piston.

Insert the insert 7 into the lower head of the connecting rod, while the retaining protrusion on the insert must enter the recess in the lower head of the piston.

Insert the insert 1 into the connecting rod cover 2, while the retaining protrusion of the insert must enter the recess in the cover.

Lubricate the cylinder, piston 4, crankshaft connecting rod journal and bearings 1 and 7 with engine oil.

Rotate the piston rings so that the locks of the compression rings are at an angle of 180 ° to each other, the locks of the oil scraper rings are also at an angle of 180 ° to each other and 90 ° to the locks of the compression rings, the lock of the oil scraper ring expander is at an angle of 45 ° to the lock of one from the oil scraper discs.

Turn the crankshaft so that the connecting rod journal of the cylinder in which the piston is installed is at Nm.t.

Insert the piston with the connecting rod into the cylinder, while the inscription: "Front" on the piston boss must face forward of the engine (towards the camshaft drive).

In order not to damage the cylinder mirror, it is recommended to put bushings made of soft material (for example, cut rubber or plastic hoses) on the connecting rod bolts.

Using a special crimp, squeeze the piston rings and push the piston into the cylinder with light blows with a hammer handle, while the crimp must be firmly pressed against the block, otherwise the piston rings may break.

Move the piston down so that the lower head of the connecting rod sits on the connecting rod journal of the crankshaft, remove the hose cutters from the connecting rod bolts.

Install the connecting rod cover 2 on the connecting rod bolts, while the ledge "B" on the connecting rod cover must be on the same side as the ledge "A" on the lower connecting rod head, and the cylinder numbers stamped on the connecting rod and the cover are located on one side.

Завернуть гайки шатунных болтов и затянуть моментом 68–75 Н•м (6,8–7,5 кгс•м

2. Screw in the connecting rod bolt nuts and tighten to 68–75 Nm (6.8–7.5 kgf · m).

3. Install the remaining pistons with connecting rods in the same way.

4. Rotate the crankshaft several times, it should rotate easily, without jamming.

Dimensional groups of pistons, connecting rods and pins

Pin diameter, mm

Hole diameter, mm

Marking

 

in the upper head of the connecting rod

in the piston boss

finger,

connecting rod and piston

piston

25,0000-24,9975

25,0070-25,0045

25,0000-24,9975

White

I

24,9975-24,9950

25,0045-25,0020

24,9975-24,9950

Green

II

24,9950-24,9925

25,0020-24,9995

24,9950-24,9925

Yellow

III

24,9925-24,9900

24,9995-24,9970

24,9925-24,9900

Red

IV

Nominal and maximum permissible dimensions, fit of mating parts of the connecting rod-piston group of the engine mod. 402

the name of detail

Nominal diameter, mm

Name

mating parts

Nominal

diameter, mm

Piston

92,0 +0,048

92,0 -0,012

 

 

 

 

Cylinder liner

92,0 +0,084

92,0 +0,024

1 repair size

92,5 +0,048

92,5 -0,012

1 size

92,5 +0,084

92,5 +0,024

2 repair size

93,0 +0,048

93,0 -0,012

2 size

93,0 +0,084

93,0 +0,024

Upper piston

compression ring

2,0 -0,012

height

Piston

2,0 +0,075

2,0 +0,050

groove width

Lower piston

compression ring

2,0 -0,012

height

Piston

2,0 +0,075

2,0 +0,050

groove width

Piston

oil scraper ring

0,7 -0,04 x 2+3,5 -0,1

height of two discs

and expander

Piston

5,0 +0,055

5,0 +0,035

Piston pin

25,0 -0,01

Connecting rod

25,0 +0,007

25,0 +0,003

Piston pin

25,0 -0,01

Piston

25,0 -0,01

Bushing top

connecting rod heads

26,27 +0,145

26,27 +0,100

Connecting rod

26,25 +0,045

Retaining ring

piston pin

2,0±0,03

thickness

Piston

2,2 +0,12

groove width

Connecting rod bearings

61,5 +0,019 – 2 (1,75 -0,005)

61,5 +0,019 – 2 (1,75 -0,012)

Crankshaft

58,0 -0,02

Connecting rod

36,0 -0,25

36,0 -0,35

bottom head width

Crankshaft

36,0 +0,1

connecting rod width necks

Nominal and maximum permissible dimensions, fit of mating parts of the connecting rod-piston group of the engine mod. 402

the name of detail

Clearance, mm

Tension, mm

Utterly

permissible, mm

min

max

min

max

gap

size

 

 

 

 

Piston

0,024

0,048

0,25

91,5

Piston

92,15

гильза

1

repair size

0,024

1

repair size

0,048

1

size

__

1

size

0,25

1

size

 __

2

repair size

0,024

2

repair size

0,048

2

size

 __

2

size

0,25

2

size

__

Upper piston

compression ring

0,05

0,087

0,15

2,1

groove width

Lower piston

compression ring

0,05

0,087

0,15

2,1

groove width

Piston

oil scraper ring

0,135

0,335

Piston pin

0,0045

0,0095

25,01

diameter

top

heads

connecting rod

Piston pin

0,0025

0,0025

Bushing top

connecting rod heads

0,075

0,165

Retaining ring

piston pin

0,17

0,35

Connecting rod bearings

0,01

0,063

Connecting rod

0,25

0,45

Dimensional groups of cylinders and pistons

Group

Cylinder diameter, mm

Piston diameter, mm

 

 

А

nominal size

92,036 – 92,024

nominal size

92,000 – 91,988

1 repair sizeм *

92,536 – 92,524

1 repair size

92,500 – 92,488

2 repair size **

93,036 – 93,024

2 repair size

93,000 – 92,988

 

 

 

Б

nominal size

92,048 – 92,036

nominal size

92,012 – 92,000

1 repair size

92,548 – 92,536

1 repair size

92,512 – 92,500

2 repair size

93,048 – 93,036

2 repair size

93,012 – 92,000 

 

 

В

nominal size

92,060 – 92,048

nominal size

92,024 – 92,012

1 repair size

92,560 – 92,548

1 repair size

92,524 – 92,512

2 repair size

93,060 – 93,048

2 repair size

93,024 – 92,012

 

 

Г

nominal size

92,072 – 92,060

nominal size

92,036 – 92,024

1 repair size

92,572 – 92,560

1 repair size

92,536 – 92,524

2 repair size

93,072 – 93,060

2 repair size

93,036 – 92,024

 

 

Д

nominal size

92,084 – 92,072

nominal size

92,048 – 92,036

1 repair size

92,584 – 92,572

1 repair size

92,548 – 92,536

2 repair size

93,084 – 93,072

2 repair size

93,048 – 92,036

* 1 repair size increased by 0,5 мм

** 2 repair size increased by 1,0 мм