Adding to what mitch said... do not poke a hole in the gasket (I've seen it done), blocking that port forces coolant around the cylinder jackets to the back of the block, then up through the back of the head and out the front of the head into the intake. with a hole there it would flow only to the front cylinders and the back of the engine would get very hot while the front cooled too much.

On a side not those are very thick gaskets and will dramatically reduce compression on a 318.