Well about 3 months ago I bent a valve and was here asking about Piston to valve clearance specs and you guys helped me out a lot. I reassembled the head with just the weaker inner springs and then stacked up .100" of feeler gauges under the rocker tip and turned the engine over...Everthing was fine and with this method I was about to determine that I had closer to .125" before contact. Fast forward to today, after reassembling the heads with new springs I drove the car until it got up to 180 and WACK it did it again. After disassemble I noticed that on the valves there was some metal transfer and took it and the head to the machine shop where I was told..."We have your guides too tight". Morral of the story I guess is to check everything that comes out of your local machine shops. I would have been driving my car for the past 3 months if not to thier mistake.