I have a 87 na with a pineapple atlernator relocation kit. I just switched back to the stock main pulley from a racing beat underdrive pulley and i just bought a custom higher output alternator.
(i'm running a haltech e8 with a electric fan so i thought upgrading to a 100 amp alt would be a good idea)(the stock alternator needed replacing)

With the stock main pulley i am just destroying belts. I was using 15375 but when i was at autozone all they had was 17380 that fit. I keep destroying belts but every time i put a new one on i get about 5 miles out of it.


Any ideas?

The alternator is the stock case but it has a different internal parts.

 

^^^ use the right belt????

 

i called pineapple
the guy said to measure it myself so i did

 

And what are you going to do with the underdrive pulley? Sell it?

Just make sure the belts/pulleys are aligned with each other is my best guess as to what makes the belts break. Plus having the right tension. Not tooo much , not toooo little. Just right.

 

If you are constantly destroying belts, always check pulleys for any burs or anything that could eat through a belt quickly. When I bought my TII, I went through three belts pretty quickly. I removed a slight burr on the water pump pulley and all has been well since.

 

yeah i wanna sell the underdrive, Ill try cleaning the pulleys.

 

Look at the belts on the engine,with the engine running.This is to see if the pulleys are aligned right, on the alternator and the Engine.I am thinking they Aren't..and If they Aren't, the Belts will snap like twigs,,Say 5 miles.

 

I agree. 5 miles isn't a long time, so watching the belts with the car running, you should see any fluctuation in the belt from unalignment. And pretty much see the destruction and where its coming from.

 

I noticed the spacer was a little harder to get in place but i didn't think it would be that much to disrupt the alignment of the belt.

 

The spacer should be on the BACK part of the alternator,not the Front.

 

Yep, the spacer is in the back and everything seems to be tight.

 

I one had that exact same problem. I'd break belts after just a few minutes. I looked at my pulleys very closely and one of them had a small bur. It didn't even feel like it could do anything. I filed it smooth and never again broke another belt. I don't even know how it got there. I probably had a tool gouge it when I was trying to pry an old belt off at some point.