There have been reports from our customers of increased problems installing oil rings on pistons and into the cylinders without the oil rings "popping off' or out of the groove. Our examinations have shown us this is generally occurring on pistons in which the land or ledge located below the oil ring and over the wrist pinhole is not machined but is left as it is cast. This ledge which the oil ring sets on over the pin is.070" smaller in diameter than the diameter of the piston 90 degrees to the pin. The photograph below illustrates the area in question.

We have found if the expander gap and rail gaps of the oil ring are installed In the piston skirt area, and staggered, rather than in the piston pin area the installation is much easier.

(P65)