Update on motor,
saturday at work we took the other head apart and no broken springs on it either. All locks, retainers, etc are Good yet.
Tested all the springs at 1.900 install height and they all tested 130 to 135 closed and 235 to 240 open.
So I don't believe there was a spring issue that caused this.
We are still leaning towards just a fatigued valve.
The springs are a wearout item and had a long life cycle in this motor so they will be replaced on the rebuild
but just wanted to update the post.

Next step will be to inspect block and cam. I did find 2 pistons that the top ring was pinched in the groove. The cylinders are the one that the broken valve was in and the cyl that the 2 valve pieces went into. Cyl #5 and #2

More to come later, David