One of the upper timing cover bolts does see oil,that O-ring is to seal the bolt to prevent oil from seeping past the head of the bolt, the o ring fits into a groove machined into one of the bolt holes on the upper timing cover,and that bolt has a different shank on it compared to the other upper timing cover bolts, It is one of the bolts on the right side[intake side] of the timing cover as you are standing in front of the vehicle, looking at the fire wall. [left side proper]