Cam gear meltdown

[dontpush86]

My friends car is going through rough times right now. The ribs on his timing belt stripped off, right at the bottom of the crankshaft where it mates with the gears on the crankshaft.
when i went to install a new timing belt i found that the camgear had been severly warped. 30 min in our oven at 500 degrees and a few dozen bangs with the hammer brought his cam gear back into decent shape...almost perfect but not quite. after running the motor without any other belts. solely the cam the crank and the tensioner, we found a humming or whining sound that didnt seem quite right.
What would cause a cam gear to warp and the belt to strip? What are the odds the humming sound is being caused by the belt tensioner...the tensioner bearings dont sound perfect when spun with your hand.
any info would be great. and also, he had just had the oil changed earlier that day. the oil level is perfect.

 

[Aricjm15]

there might be some kind of mechanical dammage
somthing may have prevented the cam from turning, like if the car has ever been overheaded, and the head is warped that would cause some issues, but the car would run like total crap if that were the case

 

[AZDriftR]

well the gear spins at a very fast rate so what might look straight to you might be bent slightly just enough to rub the belt. this would cause the belt to loose teeth, and would also cause major heat increase on the cam gear which would make the gear warp.