I have not had the problem with my Magnum R/T, but have heard of valve guides falling out. I looked it up on Google and found a numbe of references to valve seats falling out, but no references to valve guides failing. The only mention of a cause for the failures that I culd see is excessive idling. Does anyone know anything about this problem. I just want to make sure I don't do something that would exacerbate the problem on my Magnum.