Really? The physics says the damage comes from the valve bouncing, not from bouncing because the closing rate is too quick, but because the springs don’t have enough load to let th3 valve hit the seat once and not bounce.
It also beats the crap out of the locks, the groove in the valve and the retainers.
It has ZERO to do with the closing side of the lobe. It’s a control issue.
This lie has been around forever, and it was started by cam companies that were behind in their R&D, and when their junk was getting outrun, they claim the other cam grinders cam was a part breaker.
BTDT. I was there, doing this **** when Edelbrock released the first valve spring that was 300 pounds at 2.000 installed height. And all the ignorant fools who though that spring loads were killing parts were proven ignorant. The smart guys bought them and didn’t say a word. The idiots and posers kept using 200, maybe 220 on the seat and kept beating the hell out of their valve train and valve jobs because...well...because they had to be right. They weren’t.
So the fact is, the closing side of the lobe can’t be “too fast” and cause valve bounce. I can take a stock lobe, use the wrong spring and duplicate the results.