For piston rings, Total Seal gapless rings (RM269035, $175) were selected. Although more expensive than conventional piston rings, they have a super-low 111/42-percent leak down. For an engine equipped with regular rings, expect a leak-down figure in the area of 8 percent. Every little bit helps, and any compression that stays above the rings means horsepower; any that leak down end up in the crankcase. This photo shows the rings required for one piston.