squealing belt

Got a '70 Fastback Mustang with a 351 Windsor C4. Finally got it running consistant and strong with the exception of a squealing belt when I nail the throttle to wide open. I'm running one belt which runs the crank, fan and alternator. That's it. No accessories here. I've read that the pulleys can get "glazed" and that I should rough them up with a scotch brite pad or something. The fan pulley looks pretty shiny with the belt off. I can't get anymore tension on it since the tensioner has only one position when bolted in place. It is off an 89-93 5.0L

Do those tension pulleys lose their bite after time? Should I replace it with another belt too? It seems fairly snug when in place but for some reason that belt is slipping causing the squealing I guess. The only time it does it is when I drop the hammer. Very annoying and embarassing. Any help please? thanks.....dave

Is this a V-Belt or a multi-groove? Are you using the later 5.0L tensioner?

First question... if it is a 5.0 set, up on your engine, do you have the correct water pump rotation?

When illiminating all the other accessories with a 5.0 wide belt set-up, if I remember correctly, the water pump rotates in a different direction then the normal 5.0 set-up, because the belt is routed around the pump differently then a standard 5.0.

If it is spining backwards, that can be your issue because the pump must work a lot harder to spin as the rotor in the pump is designed to spin in only it's normal direction. The harder force, means the belt may slip under the heavy load.

Easy way to tell, are you using the 5.0 style fan, or the one that goes with that year engine? Then which pump are you using, the one for your engine or the one for a 5.0?

Originally Posted by Mikes66

First question...

No, that's the second question...

...if it is a 5.0 set, up on your engine, do you have the correct water pump rotation?

Good question. I guess we have to wait for him to get back with his parts useage.

Just a note on these self adjusters. If you look really close, there will be an arrow pointing to and between two lines where the pulley arm rotates. As long as the arrow is within those two lines, belt length and tension is correct.

Ok. I should have been a bit more specific. All very good points which I have addressed with the car. I did not build the motor but here's the deal. When purchased, it had a standard rotation pump on it that may have been froze up. Anyway, I thought that was incorrect given the single / serpentine belt theory / application (Not a V belt) so I purchased a reverse rotation pump. That did nothing to move the coolant. It is now back to a standard rotation as the belt runs CLOCKWISE around the TOP of the fan pulley driving it clockwise then straight down and around the crank pulley, back upward to the alternator where the tensioner is located which pushes the belt down in a bolted position creating the tension. It's possible the reverse pump would work if I route the belt UNDER the fan pulley which would drive it COUNTER CLOCKWISE. (right ?)
It is a multi grove belt about 3/4 of an inch wide. The crank pulley has the corresponding groves but the fan belt pulley surface is smooth. Running the stamped numbers on the tensioner, it is for a 5.0L 89-93 Mustang or close to those years if I remember correctly. The motor runs a consistant 190 degrees while out and about and the coolant is moving in the radiator while running.

A photo of your set-up would be a great help, but two more points....

The belt must go around the water pump at least 5/8ths of the way, or it will not have enough surface contact. Your description suggest only 1/2 of the pully is in contact, and your belt is on the wrong surface.

The belt only has groves on one side. When it goes around the water pump, is the groove side in contact with the pump, or the flat side?

If you had a power steering pump, I think your set-up would work. But you don't. I think mininum you need 4 pullies and one idler.

Sounds like you may need to cut your losses, and get a regular V-Groove set-up.

Thanks for the help. When the groove side of the belt makes contact with the fan/pump pulley, it makes contact with almost half the pulley when the belt tensioner drives the belt downward in position. The belt comes down from the alternator pulley, the tensioner pulley is pushed down and bolted in place which drives the belt down causing it (the belt) to run almost straight across in a horizontal line from left to right if standing in front of the car to the pump pulley, over the top of the pump pulley then down to the crank pulley. Back up to the alternator.

I'll try and post pics of this mess. My camera hit the deck at a car show two weeks ago and works about half the time. Kinda like my car!! Thanks for all the input guys. Livin' and learnin'...dave

If the only accessory you are running is an ALT, you may have to revert to the system used during the mid-eighties, i.e. a multi-rib belt (with STD rotation WP- no tensioner) to drive the ALT. The other accessories were driven by a v-belt.

Tension is arrived by adjusting the ALT as with a V-Belt setup, but the ribbed belt allows no slipping.

You may be able to retain what you have by using an idler pully (FRP) to draw the belt out as shown on the below photo (70.5" belt).

Need the photo.