mr bill

I have a GM 3.1 V6 that I believe is out of a 94 Pontiac Grand Am and is now transplanted into an off road car. It has been a very good runner, and actually still is though a little noisy on startup. I know that while I was out playing one day I over revved it a couple of times. It now has a lot of valve train noise on startup. It does go away after a time and a cold startup is much worse than a warm start. My question is, did I collapse the lifters? This might make sense since the noise goes away with oil pressure. What else could I have hurt that would quiet down after a bit? Is it time for the back up motor? Suggestions?

Thanks in advance.