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I just put together my 70 Impala, it's almost time for Car Craft Nationals up here in Minnesota, and I cant get a belt to stay on my motor. I kick er down n she say's peace.its the belt that runs the alt, and water pump. why does it do this do i have it too tight or too loose, i thaught i had it tight enough but i dunno its blown 2 off and snapped one.
I would check the alignment of the alternator, if its not aligned straight with the rest of the pulleys it will throw the belt off. Also make sure that you get the bolts tight on the alternator and has lock washers it could be sliding on the bracket. Be carefull not to over tighten though it can strip out the aluminum housing on the alternator. I know from personal exsperiance lol.
If you stand at the side of the fender, you can sometimes just eyeball down the belt line and see where the pulleys aren't lined up. If they look close with the naked eye, use a straight-edge to verify alignment (not with the motor running :eek: )
A worn alternator pulley will throw belts. the groove gets too wide and the belt gets whipping. You'll see a ridge on the inside surfaces of a worn one. The other pulleys are larger diameter and don't wear as fast.
Hey 70imp I had this very same problem on a 71 chevy truck I built with a bb every time I stuck my foot in the carb and she torqued up off came the alt belt. You need to go to a slightly bigger pulley diameter this will solve your problem, if in fact the alignment is correct.It may sound tachy but I used an electric motor style pulley and bored the inside out and keyed it to fit the alt. shaft.I'm a machnist so easy for me to say but you could get this easy task done at any machine shop done for probably around 20 to 25 dollars and get the pulley at any hardware,or electric or farm store. Try it it well work. wjr