4.2l stuck tensioner bolt
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When I replaced mine when I was getting a squeal eons of years ago (found out it was the 4th alternator into it), I replaced it. It was on there, and I used brute force to get it off. Felt like it was going to snap, but it didn't. It's actually a solid bolt. Don't know what grade it is, but it would take a LOT to break it.