4.3.1. Check of a technical condition and repair of the block of cylinders
Before check of a technical condition of the block of cylinders it is necessary to clear carefully it of dirt and oil.
The Konusnost of cylinders is checked by means of a nutromer in several belts:
— for GA type engines at distance of 20 and 100 mm from the top plane of the block;
— for SR type engines at distance 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 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 with a head of the block of cylinders makes 0,1 mm.
When grinding a surface of interface of the block with a head of the block of cylinders removal of metal no more than 0,2 mm is allowed.
Admissible ovality of cylinders no more than 0,015 mm.
Admissible konusnost 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 of 0,20 mm.
The 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 cylinder mirror (0,015 — 0,035 mm) — an allowance on a honingovaniye (0,02 mm).
If one of cylinders demands boring, it is necessary to chisel and 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 cranked shaft for increase of rigidity of the block of cylinders and tighten bolts of their fastening the set moment. Boring carry out in some passes, removing no more than 0,06 mm of metal for one pass. After polishing and boring carefully clear channels of the block of cylinders for oil and cooling liquid. Check size of not planeness of interface of the block with a head of the block of cylinders.