3.0 timing belt tracking issue

[Ahlem]

1993 3.0 is getting a routine maintenance timing belt change.
The timing belt tracked rearward and started shredding itself on the rear edge when test-run in the garage.
One shoulder bolt on the passenger side at the tensioner was bent and replaced by a used one.
Is there a typical issue with these things that we can be made aware of and what to look for? Nothing seems amiss otherwise and seems pretty straightforward. I've done Audis and BMW's in the past without any issue.

 

[Ahlem]

OK since we (my son actually) are the only ones who ever had this problem, after replacing the shoulder bolt that was bent slightly, everything checked out OK and the second timing belt has about 1200 miles on it and is doing fine.

 

[YFZsandrider]

It's been a while since I did a timing belt on a 3.0, but if I remember correctly there are belt guides that go install behind the camshaft pullies, and they are slightly dished so you have to index them correctly. If they're installed backward, they may cut into the belt.

Where is the belt damaged?

 

[Ahlem]

The trailing edge was shredding, about 1/4".
The cam pulleys have a lip on the front of one and the back of the other to keep everything in alignment. This situation was caused by the bent shoulder bolt. I had a similar situation once on a BMW m20 motor where the axle on the tensioner pulley was staked on like a rivet and began to break loose and pushed the belt forward and rubbed on the inside of the timing cover.