I recently swapped the intake manifold on my 318 Poly to go from a 2-BBL to a 4-BBL carburetor. Pardon me for not knowing the exact terminology but I noticed that in the cavity where the water and coolant passes through the heads that there's a thin metal rod (about the diameter of wire clothes hanger) that runs through it. What is it and what's it for? On one side it seemed dislodged from where it was supposed to be (comparing it to the other side). You can see it circled in this picture.