Figure 12-15.Piston assembly.
Figure 12-16.Cam-ground piston.
The piston is kept in alignment by the skirt, which is
usually cam ground (elliptical in cross section) (fig.12-16).
This elliptical shape permits the piston to fit the cylinder,
regardless of whether the piston is cold or at operating
temperature.
The
narrowest
diameter
of the piston is at the piston pin bosses, where the piston
skirt is thickest. At the widest diameter of the piston, the
piston skirt is thinnest. The piston is fitted to close limits
at its widest diameter so that the piston noise (slap) is
prevented during the engine warm-up. As the piston is
12-15