My coil went out in my DD 318 65 dart & made it backfire which blew a hole in the muff & people think there is a killer engine in there now. For more power first would be to attack the most restricted part of the overall "air pump" which is usually the exhaust system. That'd give you more power & a less restrictive muff(s) would definitely sound more powerful. That'd be a much better plan than just a cam change with a thumpy idle