Thrust Faces and LubricationPistons have major and minor thrust faces and unfortunately the minor thrust face usually gets most of the oil and lubrication. If you consider the oil slinging off the crank at the rod journal, the source of oiling for the cylinder, piston, rings, and pin, it will be apparent that the right side of the cylinder catches most of the oil (facing a clockwise rotating engine) with the left side of the cylinder in the shadow of the rotating rain storm of oil. If it wasn’t for the tip of the piston skirt dropping below the bottom of the cylinder, very little oil would find its way to the major thrust face of the cylinder. People do cut the piston skirt tips off to save weight and usually successfully. I always check that at least part of the piston extends below the cylinder @ bottom dead center.          |
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