Alternator belt problem

[Chevygold]

Can anyone explain why my truck is shredding the alternator belt with painful regularity? Standard 350 set up with the alternator on the passenger side, first indication is belt squeeling then silence and no charge!
I've polished the pulleys with fine emery in case they were rough after standing for a while but no joy, these belts are difficult to obtain in UK as they are a section not commonly used over here.
I think it's the original alternator so not a hugely uprated one which overloads the drive.
Starting to get frustrated as I can't go any distance before the belt fails, latest ones were mile maker by Continental so guessing they should be reasonable quality?
Thanks
Graham

[Chevygold]

Forgot to say I checked alignment and the pulleys are in line.
Graham

[VileZambonie]

Year make model and pics of your setup would be helpful. What part # belt are you using?

[Chevygold]

Sorry Vile '76 C10 Cheyenne SBC 383 alternator on Passenger side, belt CONTINENTAL 15445MK Mileage Maker I'll try to post a picture in the morning.
Graham

[JohnnyPopper]

Strange...

Is that the same brand you've used with painful frequency?

Could be a bad production run if so.

Change brands maybe?

You're not over tightening are you? I'm sure there is a inflection gauge that will give you the range somewhere...

[VileZambonie]

Belt you are running is for Fan, Alternator And Air Pump; Automatic Transmission; Without Air Conditioning

[JohnnyPopper]

Per VZ, a very common belt for many years.

You need to look for other factors: over tightening, loose tightening, oil saturation, bad run on manufacturing, mice, rust, oh wait...

Maybe a warped or splitting wheel surface?

Pics would be great!!!

[Chevygold]

Hi All, here's some photos. Like I said pulleys all in good condition, polished with fine emery just to be sure, no splits or wobbles

[Chevygold]

You can see how worn the belt is by how deep in the pulley it is, looking at the fan it looks like a 12SI so it has been upgraded, I'm running an electric fan so that's a bit less load on the belt, alternator spins freely with the belt off without any rumbles from the bearings, belt tension tight enough not to slip and scream but not so tight it kills the water pump!
The alternator belt on my '70 Corvette has been on since I got it over 5 years ago without any issues so I know they can last longer.
Are there alternative pulley sizes available? thinking a slightly larger one would help with more area for the belt to grip on.
You can see all the rubber dust from this belt all over the front of the engine.
Thanks
Graham

[MIKE S]

I would like to see a good picture of the alternator pully groove with the belt off. I suspect that the groove could bee worn. In fact check all pulleys for wear. Should be a V with no step wear.

[Chevygold]

Hi Mike, I'll have a look but I'm pretty sure that's not the case, the pulley has no step that I could feel and a new belt sits properly in the V, the belt that is on there in the pictures has gone from 12mm wide to 7-8mm so sits low in the V probably bottomed out in the bottom of the V so has no chance of driving the alternator properly.
Thanks
Graham

[VileZambonie]

7448 V-Belt is what you want.

[bd]

I'm curious, how many belts run between the water pump pulley and crank pulley?

Adjust the belt tension by hooking the alternator fan with your fingers and rotating it using all of your hand and wrist strength.  The belt is properly adjusted when the alternator pulley no longer slips.  This is the best method of tensioning v-belt-driven alternators/generators on virtually any automotive/truck application.

[MIKE S]

Now that I look at your pictures again, it looks like the Power steering belt is only going around the water pump and not the crank pulley. If that is the case I believe that it is causing the alternator belt to carry to much load and causing the belt to slip. 

[bd]

Only one belt connecting the W/P pulley to the crank certainly is of some concern since that single belt wraps only about 1/4 of the W/P pulley.  If you add an upgraded alternator with greater output into the mix(?) belt load increases even more, potentially overwhelming a single belt in spite of the fact that the fan has been eliminated.  So the failures may actually pivot around both the belt dimensions (length, width, angle) and the belt routing configuration.

Properly fitted belts should ride up to about 1 mm proud of the pulley grooves.  When all is said and done, fitting the engine with the correct, properly tensioned, and appropriately routed belts likely will remedy the cyclic failures you've experienced.