alternator belt

[86TransAm350]

is it completely unusual that i have to use a 435k5 belt when my car calls for a 450 cause a 440 wont even fit.....like its a half inch top big and a 450 is wayyyy to big....and my alt is sitting at the top of the bracket.....the guys at autozone said that its routed wrong and its not rocket science to put one of those on it only goes around 3 pullys.....but still....i had a 435 on there and it snapped....i think i had it too tight...cause it was squeakin forever .....and there were rubber shavings like caked all over the intake and stuff....but i thought it wasnt that tight but i guess it was so im just gonna use another 435 and just loosen it a bit

they also said that it could be my auto belt tensioner...or something ....i didnt know anything about that......
is this unusual????/

[tabahr]

They didn't put 350s in 3rd gens until 1987. You car is not stock? I had an 87 with a 305 and it didn't have a serp. belt, therefore there was no tentioner. I didn't think they used serp belts until 1988. I think(not posative) my 87 car had 3 belts. one for the alt, one for the air and one for the PS. But, there definitely were not any tensioners.

If your engine is indeed a 5.7 liter, you need to find out what year it is and get the correct belt.

[Joe 1320]

I've even seen the alternator and bracked swapped from the donor car making it a real bear to find the correct belt. Ya never know what people have done. I take it you don't have the original belt?