To measure the working clearance of pistons, measure their diameter and record. Now, to determine the working clearance, you need to measure the diameter of the cylinder bore as follows.
Using a cylindrical dial indicator, measure the diameter 10 mm from the top edge of the hole and then 10 mm from the bottom edge of the hole.
Take an additional measurement in the middle.
Carry out the above measurements in the longitudinal direction of the block, and then again at the same levels in the transverse direction of the block. Write down all six results.
If sketches similar to those shown in the figure are made, then for greater clarity, the measurement parameters can be written next to each other. The difference between the top and bottom measurements indicates compaction. The difference between the longitudinal and transverse measurements indicates ovality (out-of-roundness). Nowhere should the deviation from the nominal size exceed 0.08 mm.
All engines also have pistons in two oversized sizes and the block needs to be ground down accordingly to the nearest size.
Measure the cylinder block in the longitudinal, transverse and diagonal directions.
Do not use a thickness gauge with a thickness of more than 1 mm. Before starting the measurement, check that the surface of the cylinder block is perfectly clean and that there are no foreign bodies between the thickness gauge and the surface of the block.
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