Now it's time for pistons and rods. Before slipping in the slugs, we checked the end gap on the rings. In our naturally aspirated street/track application, Oster recommended going with .018-inch end gap on the top and second rings. Engines that will see boost or nitrous require more end gap. Oster suggested running between .020 and as much as .032 on some special applications. Check end gap by carefully sliding each ring into a bore and squaring it off about 1-inch down. Then use a feeler gauge to check the gap. If you need to open up the gap you will have to grind the end of the rings using a ring grinder.