I bought a set of Performer 5.0's from a friend for a biuld I am doing now. I know for a fact these heads had no more that 500 street miles and less than 10 passes. Oil was changed after his break in and twice in between. Long story short, after I bought them from him he had a family member help him remove the heads and family member rounded the hex on the head bolt adjacent to the booster. I had to go over and cut the head off the bolt to get the cylinder head off. Lucky for me, I knicked a valve spring with the die grinder. I wasn't planing on disassembling the heads because I knew their history, but after hitting that spring I needed to replace the springs. As I disassembled the springs I found the valve stem tips were deteriorating (pitting and burring). So now I needed to replace the valves too. I had a custom cam grinder helping me get the parts I needed(not crap), he contacted Edelbrock and found out who had manufactured thier vavles and springs. He found out Edelbrock uses the cheapest valve and springs they could find. I also found the spring install height varied drasticly (not shimmed properly). To replace everything I needed it would be a couple hundered dollars. I replaced the springs and got my money back from my friend.
Now I have a set of RPM's that I ran on my bracket car that I installed out of the box a couple of years ago. Took them off and disassembled them to inspect them for some of the issues I found in the 5.0's. The valves were better not great, lower line of Manely. The springs, Junk again, shimmed improperly again, and there was no spring cup at all, just a hardened shim. Ohh. the seals from both pairs were junk (Advanced Auto parts store crap) and the locks from both pairs were very soft and were distorted where the retainers were.
I am stuck with the RPM's so I had to have the spring pockets machined for cups and bought new valves, springs, cups, retainers, locks and seals for the tune of $500 (good parts).
Now think about that, $1100 for box stock RPM's and another $500 for good parts, that's $1600 for a set of RPM's (not including machining). Thats for a set of heads that have not been updated in years.
I could have gone to Camshaft Innovations and gotten a set of Trick Flows or Canfields with all the same good parts for just a couple bucks more and no heads aches.