No Sean, I am not referring to the bolt holes but the coolant passages. Now that you mention the casting being thin there, I can remember JD saying something about some heads being able to mod & some being too thin. As I said it was kinda stopgap for circle track engines-may not be desirable on the street-"redneck engineering","rigging" maybe, esp. being the cost of aftermarket heads are really not that bad(but too much for roundy racers). I am pretty sure the hole drilled was kinda small, I think a coolant passage was tapped into the rear of the intake(external, intake drilled & tapped & a coolant hose from one side to the other). It has been a while & the old memory ain't what it was-but I know I saw them on engines that worked-but I got no idea how well on the street. Seems I can remember a leaker also that we put iron heads back on. Brian
