I had a problem cooling my 65 Barracuda Formula S and could not figure it out for a long time. Then one day I decided to check the coolant (anti-freeze) concentration. It was almost 100% green antifreeze (Prestone makes a hydrometer like gadget that checks this). When I dropped the concentration to 50/50 things cooled down. I know it is a long shot, but it worked for me.