To determine the piston-to-cylinder clearance, at what location and direction should the piston skirt diameter be measured?

1. Perpendicular to the piston pin axis, at a specified distance (usually 10 mm to 15 mm) from the bottom of the piston skirt.
2. Parallel to the piston pin axis, directly across the center of the wrist pin bore.
3. Directly across the top crown of the piston, from the intake side to the exhaust side.
4. At the very bottom edge of the skirt, in line with the piston pin axis.