I need some help. I keep throwing my alt belt when I shift at high rpm's. It's a 69 BB. The power steering is fine. The belt looks lined up am I missing something? When I drive it easy they are fine.

Had the same problem, make sure the belts are straight as an arrow and if they are you might want to go to a larger pulley on the Alternator. Jegs and Summit sell them as well as other performance parts outlets.

Thanks A larger pulley or a deep groove??

I just threw mine this weekend and it got me thinking about the load on the belt. Does your alt belt also run your water pump and fan? I think I am blowing mine due to the "quick" revs not the high revs. (Hope that makes sense) I think I blew my belt because the belt cannot take the quick rpm jump and has to pull all of that fan weight that quick. I am going to try electric fans so that my belt only runs my water pump and alternator to get that large load off the belt and see if that helps.

There are several issues after going through this about 6 months ago. The first is as Elky said - the quick revs just shocks the belt. The second is that the alternator with a standard pulley turns about 3 times the speed of the engine. If you are reving to 6K or better then do the math. Most alternator amnufacturers tell you that 18K is absolute max for their product.

I changed mine to the larger (I think 5") deep groove that summit sells for $20 or so. I had to do some machineing to make it fit properly because it is designed for the alternator that has the thin sqirrel cage type fan. I was just at the track on Saturday and revved to about 6400 and had zero problems with the belt.

With the car in gear at idle it isn't chargin much but as soon as I get above 1000 rpm it starts to provide some juice. I think it's the only real way to stop the problem for good.

Good luck....

Troy.

Typical BB problem...

I've found the best solution was to run a brand name belt (Goodyear, Dayco) and not one of the parts house generic brands. The better belts run more true.

Gates Top Cog or Goodyear Gatorback belts work wonders.
I've solved problems on my vehicles by simply making sure the pulleys were alinged and installing installing one of the belts mentioned.

Here's how we solved the problem on one of my friends cars with stock pulleys.He runs an 11:1 Roller camed BB427 that spins 6500 and runs 10.90's with 4.10's and a 3800 stall.
I took a laser pointer and layed it on the waterpump pulley and saw where it hit the other pulleys and shimmed from there.Next we installed a Top Cog belt, end of problem.

If you have chrome pulleys it isn't going to work.

Thanks for all your help. I will try the the tips

I bought my car in 1987, it had a Goodyear belt driving the Alt, WP and Fan. I still use the same belt, I tried getting a new one, but so far any new belt I install flys off. I guess hwen this belt finnally gives up I will need to adress this.