The stem would come out of the valve head and the head of the valve would drop into the engine. Severe damage to the head both times. Ruined piston both times, had to sleeve the block one of the times. First time happened @ about 1300 passes w/ Manley's lower cost valves valves. Second time happened @ 1350 passes with Manley extreme duty valves. So after that I replaced them @ about 1000 passes. no more problems. This was in a W2 340 with a solid flat tappet cam. I assume that with a solid roller you'd have to replace the valves sooner. But I don't know that for a fact.
