Very different engine but it happened to my 1.5 Honda after the 2nd timing belt replacement. I did it the 1st time and no problem. A friend did it the 2nd time and said he tq'd it to 150 ft/lbs. It came loose about a month after...he just used a air wrench on it after that and it has been about 35K since then. Original bolt.
BTW it didn't come off but the bolt was real loose. It was a idiot light that alerted me I had a problem(alt?).

 

I said this in another thread and got flamed for it! For $5, I wouldn't even want to think about worrying about it. All the money we spend on these trucks and people won't go $5 for a new bolt.

 

I've seen this happen when a motor was over revved. Now, this was on a BigBlock with a ProCharger that was making 1300hp. Broke the trans coming off the transbrake @ 6000 and at 15psi of boost, Motor over revved, broke the procharger and broke the pulley off the crank. The owner of the car purchased a 3 step before the next outing.