Repair of the camshaft and replacement of its bushings UAZ-3151
Restore the necessary clearances in the camshaft bushings by regrinding the bearing journals of the shaft, reducing their size by no more than 0.75 mm, and replacing the worn bushings with semi-finished ones, followed by boring them to the dimensions of the polished journals.
On engines without bushings, restore the necessary clearances by boring holes in the block for bushings, guided by the data Tolerances of the main parts of the UAZ-3151 engine, and subsequent pressing of bushings of 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 timing gears and to the rocker shaft after grinding the journals.
Grinding the necks is carried out in centers with a tolerance of 0.02 mm.
Polish the neck after grinding.
It is more convenient to press out and press in bushings using threaded studs (corresponding length) with nuts and washers.
Semi-finished camshaft bushings, supplied as a spare part kit for one engine, have the same outer diameter dimensions as the nominal size bushings, so they are pressed into the block bores without pre-machining.
To ensure sufficient thickness of the babbit (anti-friction material) layer, the amount of repair reduction in the inner diameter of all bushings must be the same.
When pressing the bushings, make sure that their side holes match the oil channels in the block.
Turn the bushings, reducing the diameter of each subsequent bushing, starting from the front end of the block, by 1 mm.
Bore with a tolerance of +0.050 +0.025 mm so that the gaps 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, keep the distance between the axes of the holes for the crankshaft and camshafts (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 the parallelism of the crankshaft and camshafts 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.
Camshaft cams with slight wear and scuffing should be cleaned with sandpaper: first coarse-grained, and then fine-grained.
At the same time, the sandpaper 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 more than 0.5 mm in height, replace the camshaft with a new one.
Check the camshaft curvature with an indicator on the backs (on a 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.