If you're referring to that 1/4 inch hole, plugging that hole wont do jack, the centre passage is wide open to the whole internals of the coolant of the head. (EDITED)
Sorry incorrect. Of COURSE the coolant is in the head........he's speculating on whether it will "live" OK with the intake. Unlike blocking the exhaust crossover, "if it seeps" a little it will NOT be OK in this case
