[Tommy]

One more thought from one who also experienced this problem. If you put too much sealant between the header and the head, the relatively low torque on the header mount bolts will cause the header to stand out a little farther than it would with just a gasket. On my car, combination of the too thick gasket, the weight of the headers and side pipes, and the motion of the car caused the header to begin to rock back and forth until it began to leak. That was in spite of the fact that the header mount bolts were safety wired. I now use just an exhaust gasket on my 351W.