Repair of the camshaft and replacement of its bushings UAZ-3151
Restore the required clearances in the camshaft bushings by grinding the shaft bearing journals, reducing their size by no more than 0.75 mm, and replacing worn bushings with semi-finished ones, followed by boring them to the size of the ground journals.
On engines without bushings, restore the required clearances by boring holes in the block for bushings, guided by the data (Tolerances of the main parts of the UAZ-3151 engine), and then pressing in bushings of the nominal or repair size.
Before regrinding the camshaft journals, deepen the grooves on the first and last journals by the amount of reduction in the diameter of these journals in order to ensure the supply of lubricant to the camshaft gears and the rocker arm axis after regrinding the journals.
Grind the necks in the centers with a tolerance of 0.02 mm.
After grinding the neck, polish it.
It is more convenient to press out and press in bushings using threaded rods (of appropriate length) with nuts and washers.
Semi-finished camshaft bushings, supplied as spare parts kits for one engine, have the same outer diameter dimensions as the nominal size bushings, so they are pressed into the block bores without pre-processing.
To ensure sufficient thickness of the babbitt layer (anti-friction material), the amount of repair reduction in the internal diameter of all bushings must be the same.
When pressing the bushings, make sure that their side holes coincide with the oil channels in the block.
Bore the bushings, reducing the diameter of each subsequent bushing, starting from the front end of the block, by 1 mm.
Carry out the boring with a tolerance of +0.050 +0.025 mm so that the clearances in the bushings after installing the shaft correspond to the data (Tolerances of the main parts of the UAZ-3151 engine)
When boring bushings and holes in the block for bushings, maintain the distance between the axes of the holes for the crankshaft and camshaft (118±0.025) mm.
Check this size at the front end of the block.
The deviation from the alignment of the holes in the bushings should be no more than 0.04 mm, and the deviation from parallelism of the crankshaft and camshaft should be no more than 0.04 mm along the entire length of the block.
To ensure the alignment of the bushings within the specified limits, process them simultaneously using a long and fairly rigid boring bar with cutters or reamers mounted on it according to the number of supports.
Install the boring bar based on the holes for the main bearing shells.
In case of slight wear and scuffing, clean the camshaft cams with sandpaper: first coarse-grained and then fine-grained.
In this case, the grinding paper should cover at least half of the cam profile and have some tension, which will ensure the least distortion of the cam profile.
If the cams are worn in height by more than 0.5 mm, replace the camshaft with a new one.
Check the bent of the camshaft with an indicator on the backs (on the cylindrical surface) of the intake and exhaust cams of the second and third cylinders.
In this case, install the shaft in the centers. If the shaft runout exceeds 0.03 mm, straighten or replace the shaft.