4.3.1. Check of technical condition and repair of the block of cylinders
Before check of technical condition of the block of cylinders it is necessary to clear it of dirt and oil carefully.
Conicity of cylinders is checked by means of a nutromer in several belts:
— for GA engines at distance of 20 and 100 mm from the top plane of the block;
— for SR engines at distance of 10, 60 and 100 mm from the top plane of the block.
The difference of the sizes should not exceed 0,01 mm.
Ovality of cylinders is measured in two points at distance of 60 mm from the top plane of the block on two mutually perpendicular axes. The difference between the measured diameters should not exceed 0,015 mm.
At repair of the block of cylinders it is necessary to consider the following requirements.
Admissible not planeness of a surface of interface of the block to a head of the block of cylinders makes 0,1 mm.
When grinding a surface of interface of the block to a head of the block of cylinders metal removal no more than 0,2 mm is allowed.
Admissible ovality of cylinders no more than 0,015 mm.
Admissible conicity of cylinders no more than 0,01 mm.
The most admissible wear of cylinders in operation of 0,2 mm.
Difference of diameters of two cylinders: nominal 0,05 mm, the most admissible 0,20 mm.
Admissible increase in diameter of the cylinder when boring is defined by the next way:
diameter of the piston + a gap between the piston and a mirror of the cylinder (0,015 — 0,035 mm) — an allowance for a honingovaniye (0,02 mm).
If one of cylinders demands boring, then it is necessary to chisel also all other cylinders.
In case of excess of the specified admissions it is necessary to chisel cylinders under the next repair size and to pick up pistons of the corresponding diameter. Before boring establish covers of radical bearings of a bent shaft for increase in rigidity of the block of cylinders and tighten bolts of their fastening the set moment. Carry out boring in several passes, removing no more than 0,06 mm of metal for one pass. After grinding and boring carefully clear channels of the block of cylinders for oil and cooling liquid. Check the size of not planeness of interface of the block to a head of the block of cylinders.