By ring gap, in mean that when the rings are inserted into the bore, without being on the piston, there should be a gap where the two ends meet. Slide them into the bore, and "square" them up in the bore by sliding a piston down to them. When you pull the piston back out, then SHOULD be a gap where the two ends meet. You should find specs on what that gap should be. Then you need to file one end of the ring down to get to the required gap. This gap assures that there is no "bind" when it cycles up and down. I think some rings come "pre-gapped" but checking into it won't hurt any. As far as a notch on the piston itself, I'm not sure about. Maybe someone else has some thoughts. Later
Looks like the "notch" is there to keep the spreader from contacting the cylinder. The two oil rings and the spreader should fit together as a tight sandwich. Try to fit them together off the piston first so you can see how they lock in place. Then get a micrometer measurement of the assembled stack. Then you can measure the piston groove and see if you have the required side clearance. You can do this with a feeler guage too. Just place the assembled stack into the groove "backwards" (so the piston and ring look like a figure 8 from the top) and check the side clearance with feeler guages. Check a few places around the ring and piston. The spreader acts like a spring to keep the oil rings in proper contact with the cylinder. These multi-piece rings are a pain to get in but they do a better job at oil control. Best of luck - John
The spreader is the wavy thing. Two very thin rings and the spreader go together like a sandwich and make up the "oil ring". DO NOT shave off any part of the assembly. The only place you would want to file (if needed) is the end gap (as described by Bobcat). The spreader should lock together with the rings and fit into the piston groove. If it doesn't fit you might have the wrong rings. One more thing... I don't remember for sure on the thin oil rings but they might have an "UP" side. The compression rings probably do have an "UP" side, usually identified by a chamfer along the inner edge. Check your book to see if the chamfer goes up or down (sorry, it's been a long time since I've done this) . Hope this helps... Best of luck - John