Visually check the block for cracks and signs of corrosion. Repair stripped threads in holes. It is recommended to check the tightness of the cylinder block in auto repair shops that have the appropriate equipment. If any defects are found, repair the unit or replace it.
Check for scratches and burrs on the inner surfaces of the cylinders.
Figure 3.36. Places for measuring the inner diameter of the cylinder: directly under the flange (X and Y), in the center and at the bottom
Measure the inside diameter of the cylinder at the top (right under the flange), middle and lower parts parallel to the crankshaft axis (figure 3.36). Then take measurements at the same levels, but in a direction perpendicular to the crankshaft axis. Compare the measurement results with the values in the technical data. If there are severe burrs and scratches on the cylinder surfaces, or the ovality and taper of the cylinders exceed the established maximum permissible values, take the block to an auto repair shop for boring and honing. After repair, pistons and rings of repair sizes will be needed.
If the condition of the cylinders is acceptable, the wear of the cylinder and the clearance between the cylinder and the piston do not exceed the established standards, then boring is not required. The only operation that remains necessary is honing.
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Before honing, install the crankshaft main bearing caps (without bearings) and tighten the bolts to the required torque.
Figure 3.37. The cylinder surface after honing should be covered with a grid of thin lines intersecting at an angle of about 60°
Honing requires a special device with fine grinding heads, a large amount of oil, a rag and an electric drill. Clamp the fixture into the drill, secure the grinding heads and insert the fixture into the first cylinder. Lubricate the cylinder surface well with oil, turn on the electric drill and periodically move it up and down in the cylinder. A network of thin lines intersecting at an angle of about 60° should form on the surface of the cylinder walls (figure 3.37).
Keep the cylinder surface generously lubricated at all times. Do not remove the device while rotating. After turning off the drill, continue moving it up and down until it comes to a complete stop, then squeeze the legs of the attachment with the grinding heads and remove it from the cylinder. Remove oil from the cylinder surface and repeat the operation on the remaining cylinders. If the device is not available, this operation can be performed at a car repair shop for a reasonable fee. Satisfactory results are obtained using an emery wheel attached to an electric drill or even by performing the operation manually with sandpaper.
After honing, chamfer the top edges of the cylinder bore with a small file to prevent the rings from binding when installing the piston.
The entire cylinder block must be re-rinsed with warm water and detergent to remove any remaining abrasive material from honing. Clean all channels with a brush and rinse with running water. After washing, dry the cylinder block and lubricate all treated surfaces with spindle oil. Before assembly, store the unit under a plastic cover.