timing belt wear

[duncanm]

I just finished a motor and trans. rebiuld and after running for 15 min I noticed that the timing belt is drifting forward, and wearing. Is this a belt tention problem, or dose thito do with have to do with the aline ment of the pulleys?

[zukgod1]

Usually its an alignment problem, just a little dirt under one of the mounts will cause a problem.
Can you tell visually, does the cam pulley line up with the crank?