I finally have my 401 back from the machine shop and it's time to assemble. After lots of cleaning, cam bearing and crank install, I am on to the pistons. I went to install the oil rings and noticed I could not get the oil ring rails to seat all the way into the piston groove. The oil ring assemblies are designed so the rails ride on tabs on the expander, which helps keep the rails tight against the cylinder walls. Before I can fully compress the rails into the groove, the expander ends butt against each other. There is more than enough back clearance in the groove for everything to fit.
I dropped one rail into the cylinder to make sure they are the right size and they fit fine, with almost no gap. When I installed in the groove, I assume I would see a similar tiny gap, but I cannot compress enough as the expander is holding the rails out too far. I even took out my piston ring compressor and noted there is no way I will be able to compress the oil assembly to fit into the cylinder. I am guessing I need to reduce the diameter of the expander, but want to be sure I am thinking about this correctly. Anyone use these rings before? Am I supposed to fit the expander to the piston? If so, how is it done (remove material, bend ends)?