[lust4speed]

The oval shaped hole in the bracket allows the alternator to be pulled out of line as load is increased. So the bolt might be sitting in the center of the hole with the engine off or at idle, and then when you gas it hard the bolt moves over to the edge of the hole and pulley alignment goes out the window. You shut off the engine and get out and look and the pulleys look normal again because the bolt has moved back over to center.. There seems to be a threshold on the wear, I never had a belt problem and one day started throwing alternator belts. Finally found the oval hole problem and bushed the end back tight and haven't thrown another belt.

Originally Posted by torqjunki

OOps Forgot to post pic

Your PS belt should be wider. On the Gates series, the 9xxx series is correct for power steering and is about 15/32" wide, and the 7xxx is the one for the alternator and about 13/32" wide.

[455rebel]

Put the narrower belt on, no change, I am at my wits end, took a straight edge and checked all the pulleys for alignment, they are in line.
Benn doing some googling last night, found some post that said they had fan clutches to squeal just like a belt in the higher rpm, I'll change it tomorrow.
Any other ideas?

[lust4speed]

Also sometimes a straight edge doesn't work well on the pulley edges because different pulleys have different shoulder widths. Best thing to check alignment is a new piece of 3/8" straight steel tubing setting solid in the groove of the water pump pulley, and then rotating the WP pulley and tubing down on to the alternator pulley. Watch where the initial contact is made, and that will be how far the pulleys are off. If allowed to just sit in both pulleys, the method isn't any better than eyeballing the belt. We've tried all sorts of things, and the solid tubing straight gas line has worked the best for us.

[Toms bird]

Went through the same thing. Tried everything. It ended up being a Harmonic balancer in my case.

[72LuxuryLeMansLa.]

Originally Posted by Toms bird

Went through the same thing. Tried everything. It ended up being a Harmonic balancer in my case.

Now you're scaring the crap outta me! This can get expensive fast if I don't diagnose correctly! Good thing I've been collecting engine build parts for three years!

[Toms bird]

I screwed around for a couple of months. Changed pulleys, belts, repainted pulleys sanded pulleys,shimmed alt in and out. Out of desperation and I had a spare new one put the balancer on. Used the same belt and pulleys that were squealing not a sound. Factory balancer I think cost under fifty with shipping I had more than that in belts alone. I never would have suspected one would do that. It's hard to look good under 3000 rpm.

[455rebel]

Originally Posted by Toms bird

Went through the same thing. Tried everything. It ended up being a Harmonic balancer in my case.

Installed different fan clutch, same noise.
I will have to look at ballencer next, planning on pulling it all back
apart this week.
What happened to the ballencer to cause the squeal?
I don't have another one to try.
I'll have to buy one if mine is bad.
Where do u get a ballencer for a 455?
This has been a nightmare!!!

[Mike Fowke]

I just bought a GM balancer from gmpartsdirect.com. Part # 88960256. About $50 delivered.

[455rebel]

Ordered one from napa today, 40something + 15 for the seal and I will
try to install it tomorrow.
Been wrenching for over 40 years, had balencers shake, had them wobble,
seen them fly apart, never heard one squeal though.
I should have replaced the 40+ year old one when I rebuilt the 455 ,
but it looked good and I was on a budget.
It's getting worse, cranked it up today just to pull it in the shop, squealed
today just above idle, who knows, one more stomp may have grenaded it.

[455rebel]

Ok, finally, no more squeal.
Balancer did the trick.
Had to reset my timing after install, old one had slipped about 8-10 deg.
I'll never build another 40 year old engine again without replacing the balancer.
Thanks, toms bird for the post!!!

[Toms bird]

Glad that worked for you. I learned the hard way too, but it looked ok I thought.

[455rebel]

None of my gear head buddies have ever heard of this,ex dirt track racer,engineer at mahle,retired mechanic(car dealer) ,retired mechanic(diesel shop),speed shop counter man.
This must be kinda rare. Just my Luck!!!