I have this new 200 amp alt and the pulley is 1/2" smaller than OE. I went to Pep Boys and got what seemed to be a belt that was 1/2 in smaller as well, however it wont work its too short and wont fit up to alt pulley. I tried the OE belt it seems tight but when started the tensioner shakes pretty hard. Is there any harm in swaping out the pulleys?

Disregard that idea I just tried to remove orig pulley and it seems very hard. I need a belt that extends to a max of 28.5 inches. Orig is 29inches. I'll have to take the measuring tape to Pep boys tomoorow. Is this the only way????

Well, I know when I put on the belt that was 1/2 inch shorter it was a tight fit. There wasn't a lot of play left in the tensioner after it was installed. The stock belt fit nicely, but once the car started I had similar problems. After just a few seconds it started to scream somethin fierce!

Ok, I just went outside to get the actual part # from the one that is on mine.....and guess what. It isn't labeled.

I belive the first belt I used on it was 1/2" shorter, and it worked great. When I needed to replace it I found that the same belt (part # anyways) was too short, and a OE belt fit. :? I can't explain it, but that'* how it went.

Ok I took that belt back to Pep boys. For OEM the part# is 600 I had bought a 590 which was a whole inch shorter which explains why it didnt work. So I just exchanged it for a 595. Seems to be right this time. Thanx. another ques: I chgd out my 3 front plugs with the ac delco plats I had sittng in the basement because the others were wet. I didnt touch the rears but this small change allowed my car to start. If the rear ones were wet will they kind of clean themselves now. And am I hurting anything by running 3 delco plats and 3 NGK coppers?

That new alt belt started shredding on me after work yesterday. I went to Pep Boys and one of more experienced techs advised me he knows the smaller pulley is there to generate more of a charge at idle but that I should nt use it. It cause pulley alignment issues. He offered to swap the pulleys for me free of charge so I did it and went back to OEM size belt.