Squealing fan belt

I have this weird problem after i drive for a few minutes at speeds above 45-50 MPH 2000+RPM my fan belt starts to squeal under deceleration. If i get back on the gas and the noise abruptly stops. It never occurs at low speeds or short high speed jaunts. Also if i slow back down it stops after a little while.
Some things i did to stop it are:

1. Replace belt( Gates )
2. sand pulleys
3. Correct tension

This is driving me crazy, any Ideas? :?
EDIT: I started after i replaced my worn out belt.

 

guessing
intake manifold vac leak ?
bad bearing in alt, idler pulley, etc
I don't think its belt related
my 0.2 worth

 

Sounds odd. Have you made sure your belts aren't bottoming out in the pulley grove. If it bottoms out it will still squeal. I don't know, just a thought.

Kevo

 

The belts are not to tight are they?
Try rubbing some soap on the inside of the belts.
If it still screams at you start looking elsewhere.

 

I put the soap on the belt and it still did it. I pulled over after it started to squeal and i noticed it originated by the carb. If it was a manifold leak wouldn't do squeal all the time, Not just at relatively high speeds?

 

not always
in this case only on de-accel when vac is highest
try tightening up the intake bolts
is this a 258 ?
I might add could be internal carb squeal as well

 

Yes its a 258, Ill try tightening up the bolts. Is it common for A Carter YF to squeal?

 

no
that could happen with any carb, not just yours
on de-accel, engine vac is really high; and if you have a loose or bad gasket, that can create the very high pitched noise you are hearing.
when you stated only on de-acel, that was the clue for vac leak for me

 

try snugging up the manifold bolts first, they are well hidden so make sure you get them all
then try snugging up the carb nuts as well
don't overtighten, stop when your elbow torque wrench clicks

 

Thanks, I'll look up the toruqe specs and retighten them.

 

Thanks for your help JP i tightened them and the noise went away.