Alright, I'm working away on this C30 and am getting ready to put the heads back on. I have new o-rings for the oil control orifices at the front of the block. However, at the back, there are machined holes that sure look like something belongs in there. But according to the pictures I took during disassembly, the FSM, and even online parts catalogs, it remains empty. Am I correct in thinking that it gets left open, or am I losing my mind? I can't figure why they would intentionally machine a hole like that and leave it empty.
