im swapping, or attempting to swap an h23 manifold onto my f23 block. i want a bigger manifold since the tiny f22 one i have on is just sapping power from the turbo. anyway, there is a coolant passage on the block that does not line up with the h23 manifold. this leads me t my main question, what the heck does that coolant line do? where is the coolant going and can i block it off? all the writeups and tech articles ive read all indicate that its safe to block the passage on the manifold side, and that it should not be an issue.

can anyone tell me what the coolant passage may be for because i havent managed to find out yet and i dont want to block it without knowing what it is.

to give a little more info on it, if you are looking at the manifold looking into the runners, it would be the nickel sized hole on the left in the bottom corner.