To measure the piston clearances, measure the piston diameter (Fig. 90) and record the measurement results. To measure the clearances, measure the cylinder diameter as follows:
- Using a cylindrical dial indicator, measure the diameter at a distance of 10 mm from the top edge of the cylinder and then 10 mm from the bottom edge (Fig. 89).
- Additionally, take a measurement in the middle.
- Perform the above measurements in the longitudinal direction and then measure again at the same depths in the transverse direction of the block. Record all six results. The difference between the upper and lower measurement characterizes the taper. The difference between the measurements in the longitudinal and transverse directions characterizes the ovality. In all measurements, the diameter should not differ from the specified value by more than 0.20 mm.
There are oversized pistons and the block can be bored out to accommodate them.
The cylinder block surface skew is checked in the same way as the cylinder head, as shown in Figure 54. Measure the block in the longitudinal, transverse and diagonal directions. A feeler gauge thicker than 0.05 mm should not pass through.