I have a 2007 STS 3.6 , 103000 miles, last Feburary when i go down to -13 deg, went to go to work car would not start, jump forward all intake valves on passenger side bent, my question is what was the cause of failure, car ran, when it was taken apart the timing chain was loose on that side, need to pull other head as compression was below specs on that side also. Just wondering what course of action i need to take, any help would be appreciated.