Checking the technical condition of connecting rod and piston group parts

Make sure that the connecting rods are in the same weight group: connecting rods without bearing shells should not differ from each other in weight by more than ±4 g. Check for color markings of weight groups on the connecting rods. If there are no markings, compare the connecting rods by weight, using one of them as a reference.

Check the condition of the connecting rod upper head bushings. When replacing the connecting rod upper head bushing, it is necessary to align the lubrication holes in the bushing and the connecting rod head. To do this, it is necessary to shift the bushing lock by 90° relative to the hole in the connecting rod upper head (see photo).



The connecting rod upper head bushings are bored at the factory to exactly the outside diameter of the piston pins. However, the pin should be checked for proper fit to the bushing. For proper mating, the piston pin, lightly lubricated with animal fat or motor oil, should fit into the bushing hole with a simple push of the thumb. If necessary, bore the hole in the connecting rod bushing.

Check the alignment of the connecting rod head bore centers and the longitudinal bending of the connecting rod (see the figure below and the value in the subsection "Detailed technical specifications").




Make sure that the pistons belong to the same weight group, which is marked with "+" or "-" marks on the piston crown.



Check the clearance between the piston and the cylinder (see the value in the subsection "Detailed technical specifications") by measuring the outer diameter of the piston at a distance "A" from the piston skirt (see photo).



Press the retaining ring into the annular groove of the piston boss on the side opposite the arrow for orienting the piston in the cylinder, stamped on the piston bottom.


Clamp the connecting rod vertically in a vice with soft jaws, pointing the oil hole 8 of the upper connecting rod head towards you.

Lubricate the connecting rod bushing and piston bosses with engine oil.

Place the piston on the connecting rod, pointing the arrow towards you to orient the piston in the cylinder. Insert the piston pin into the piston hole until it stops against the installed retaining ring.

Install the second snap ring into the piston boss ring groove.

Assemble the other pistons with connecting rods in the same way, install the liners in the connecting rods and connecting rod caps. Temporarily tighten the connecting rod bolts.