Back to work also, tore the 64 Buick down. Exactly what I thought it was bottom of the intake there is a core plug, it is for the heat crossover for the carb. The 63 I had the same thing happen. So next nail head I get something to change. Made it from home to Arz before turning back, was just afraid it might do more damage driving that far and did not want to try and MacGyver something on the side of the road.