I had them on the car for about 1k or so rated up to .530. The cam I'm running is .510 / .500, I don't know what went wrong ? I was just crusing is 5th at about 2500rpm and it let go, no other damage though
I just thank god the locks / keepers held the valve in place.
Make sure you call them up and explain what happened. It may have been just a bad batch. I'm pretty sure a company with their repuation would be glad to send you a replacement set of springs.
I hope they make it right with me on this. I could see this happening if I was using some crazy ass lift, but I was on the mild side. If they don't, I was looking at anice Lunati set