11. In order to squeeze that extra long 6.125 connecting rod as well as a 4.000-inch stroke crank into a standard deck block the compression height on the pistons has to be quite short. So short, in fact, that the pin bore intrudes into the oil ring groove. To fix this, an oil ring support rail must be installed before the oil ring components. The support rail can’t be allowed to spin, or else the ring gap can wind up over the opening in the groove. The support rail has a dimple that must be situated so that it faces downward over the opening created by the pin bore once the ring is installed. This keeps the rail from spinning.