Belt squeal

69 C10 big block
Belt squeals at high rpm. PS pump was misaligned so I replaced the pump and brackets only to discover it's actually the fan/alternator belt that's squealing. Oh well, now I have a new PS pump.
This is a brand new belt, seems to fit well. Alternator is aligned, tension is good. Tried belt dressing, no help. I don't know what else to try. Is there a high end belt that won't slip? Or a better alternator pulley? It drives me crazy! :confused:

[IMG]https://i.imgur.com/cyNLtXB.jpg[/IMG]

Maybe a larger diameter alt pulley?

Welcome to CHR! Have you confirmed that your alternator is good? Worn bearings can cause higher load, and may cause the belt to slip. They can also emit a squeal that sounds like the belt slipping. Just a thought.

Not a great picture but, it appears to my eye that the alternator pulley is to wide and the belt is probably riding on the bottom of the vee, look to see if the bottom is shiny from where the belt is in contact. Many times a lot of these " hi output" offshore alternators come with a new pulley but they aren't sized correctly. I had this exact issue with mine. I ended up at a local rebuilder and bought a stock pulley for something like 8 dollars to match the pitch of the fan vee. problem solved for me.

along the vein of what 34_40 mentioned you may have too skinny of belt .. see if all your pulleys look to be the same size if so then perhaps go with a size wider belt .. i have`nt fooled with belts in a long but gates used to size their belts by the first digit being the width then the second 2 or three being the length .. such as a 7350 would be 7 being a standard width and the 35 being how long it was and the 0 being no fractions .. a 8352 belt would be wider and be 35.2 inches long ..