The ring endgap checked out so the compression and oil rings are installed on a new set of 0.040-over cast pistons from Egge Machine. A set of Grant rings will handle the compression chores in the 331. The expander-spacer oil ring is color-coded so it's easy to tell if it's installed correctly. The two colors should be visible and land directly above the wristpin. Two steel rails hold it in place, with the gap on either side of the wristpin (arrows). The compression rings should be perpendicular to the wristpin on opposite sides of the piston.