Usually when you see carnage like that it indicates piston to valve contact, rather than a valve failure. A typical scenario is the hydraulic lifters pump up or the springs lose control of the valves at high RPM. The piston in the cylinder hits the valve because it is open too far (lifter is pumped up or the valve is bouncing off the seat), and breaks the head off the valve. Once the valve head pops off all that carnage happens in about a half a second. Been there, done that, unfortunately...