Got my 5th equinox/torrent with bad headgaskets. Previous 4 purred like kitten after job. The 5th one I did this past weekend rattled like a mofo. After 1/2 hr it seemed to quiet down. I drove it 3 weeks ago for 1/2 hr. Ran fine. Started it on sat after work and rattle city. None of the other ones made noise. Sitting for 2 weeks should not affect the lifters that way. Maybe it’s just worn more? Who knows.