I'm only guessing that this topic has not been covered...yet. As I had previously posted, I had the pleasure of replacing the clutch a few weeks ago, drilled out the weeping hole etc..etc..etc.. Got the 2005 LT back together and have since noticed a rattling noise coming from the bellows of the beast. I have since removed the exhaust once again and replaced the gaskets. (couldn't even find the originals but I was not the first owner) I had the stethoscope on today and if my calculations are correct???? the source is coming from the cam chain tensioner pad area. Is it possible when I adjusted the valves last summer (and rotated the engine backwards) I could have caused problems inside where the guide pin travels? Is there a check valve or any other devise that could get sticky? Is anyone aware of any tricks of the trade to free this up without total disassembly ,if that is what I am into?