[troll]

Hey I saw that happen.And there was a telltale sign it was going on.In my case it was the rocker arm hitting the retainer before the stem.(damned professionals did this work for did for someone I know)The valve dropping in the hole did happen but at low RPM and it only bent the valve.There was a lot of grey looking grit on the keeper.It was a 289 and I went and got some 390 springs,retainers and keepers and put them on,no more prob.Its now my engine and it has seen 8,000 rpm.Look for the grit.