A ring positioning device has positioning elements radially adjustable on a support to fit different diameter cylinder bores. The positioning elements slide in channels in the support and are clamped to the support by knobs that have threaded shafts that slide in slots through the support and are threaded into the positioning elements to clamp them to the support. The positioning elements have protrusions or shoulders that engage the cylinder block deck and lower abutment surfaces that position piston rings in the cylinder bore. A second embodiment uses pivoted arms to adjust for different cylinder bore size with threaded rods on the arms to adjust for different depth ring placement.