First time it happened to me. Man, that's a weird sensation.

 

don't you just love it when that happens.

 

I guess the Whipple has pretty tight clearances inside, it turns backwards when I goose the throttle with no belt on it. Pretty cool!

 

The tensioner might be worn out. The belt comes off during rapid RPM drop, like during a 1-2 WOT shift or when the wheel grab after spinning. The supercharger's rotational inertia causes it to overspin the crank and the belt pulls tight on the tensioner side causing it to go slack on the idler side. More tension on the belt will help.
I struggle with belts and tensioners too.

 

Cool, I never tried starting mine with no belt on it.

 

In a past life I had a 1995 Suburban with a 454 and a Whipple, which I had bought used. At any rate, I went through at least 3 belts coming off and big $$$ before I could find a local shop that could put everything on properly so that the belt would not come off. I always wondered why the whipple pulleys did not lips on each side to help keep the belt on. Sure it might still crawl a bit but it would definitely be tougher to crawl up the lip as opposed to straight off a flat surface pulley.

 

My pullies dont have a lip, knock on wood but Ive never thrown a belt either.

 

A worn-out tensioner make sense, since it has never happened before, or the belt dry-rotted because the truck hasn't run since springtime. I am wondering if my balancer is crooked. I am on my second crank pulley, I put on a bigger one than came with the Whipple kit, and they both wobble. You can see the tensioner tighten and loosen exactly in step with the wobble. And still, it has never thrown a belt priorly. (Look that up in the MikeGyver dictionary.)

 

My lower pulley the whipple setup is wobbeling at idle but looks fine under load. It keeps throwing the belt. What is a fix? Thanks guys

 

you got a camera under your hood while driving?