When you did this "head job" did you remove the intake manifold or seperate the head from the block? if so did you follow the correct torque pattern? the intake manifold bolts have to be torque in a specific order for the manifold to set itself properly. If not you will have spillage of gas into the coolant, trust me it is something you will want to correct quickly.
Try removing you rad cap and smelling the coolant, if it smells gasy I would recheck the intake manifold. You could try some stopleak and see if it swells the seals, but imo I would tear it down again and redo.