hey guys this isn't in a truck but i have a question that has had me and my brother baffled. we put a 429 in his '78 thunderbird, the engine has been rebuilt, bored .030 over with a mild cam. it also has a wieland intake and 4brl carb if that matters. so far we have snapped 6 or so alternator belts and we can't seem to find a reason. the pulleys are lined up perfect and it still does it. the brackets are older stamp steel pieces but it is a completely factory setup. the most recent one that broke we found and it actually chewed ribs off the bottom before it broke. oh, and as best as we can tell it's not rubbing on anything.

FORDS_FORLIFE

 

Wrong belt for the pulleys or vice-a-verse-a. Make sure the belt doesn't bottom out in the either of the pulleys.

 

pulleys can ware out did ya try different pullys?

 

Did you by chance put a new water pump on this when you rebuilt it I have seen this when the hub on the water pump wasn't pressed on straight causing the belt to run off the edge of the pulley breaking it. It won't do it at idle but will when runnign at higher RPM.

 

Always make sure your belt is exceeding the height of your pulley and is not bottoming out