[DICK SPADARO]

Something doesn't look correct. My experience with valve retainer failure has been attributed to coil bind of the valve spring. Properly installed units will have only spring pressure to hold them in position and that is not enough to damage a retainer. What I think you have is a mis match of parts. There are two different springs used between early 32-50 and later version 51-53 8BA engines and the spring must match the valve. The early retainer is used with the 32-50 early springs 10 wrap and the later two part retainer is used with the 51-53 later spring 9 wrap and valve.

If you determine that you have had the wrong parts you should check your cam shaft for excessive wear or galling on the lobe.

Mac was typing while I was comparing parts. It appears you have a 10 wrap spring on a 9 wrap keeper and that is your issue.