Like most guys said, it was an alignment issue. I won't delve into all the details here, but I will say I had to experiment shimming the blower bracket. I had a suspicion that the culprit was the idler that feeds the belt onto the crank because it was not centered. In other words, the bracket edge of the idler was flush with the edge of the crank pulley. That sounds fine, except that the idler is about 1/2" wider than the crank pulley. That means the belt was not centered on the idler, yet as I cranked the engine, it tried to center itself -- thereby walking the belt over the front lip of the crank pulley.

I experimented with shimming the bracket, which is no easy task. I finally got the idler to center with the crank. Then it was a matter of shimming the blower to align its pulley with the crank pulley. In doing so, I discovered the 0.780" spacers are about 0.1" too long. This in turn, makes the two larger bolts too long.

Now I can even start the car without the belt flying off. Before, just cranking it without starting it caused the belt to walk.

But now, the tensioner is maxed out... I wonder how much the belt stretched with all this walking?

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://members.optushome.com/au/downunder1/rides/willie/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited January 11, 2001).]

 

Congrats Willie!

Are you going to snap some pictures of your setup and post them on here? Im curious to see how it looks all finished up!

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-86 IROC
Vortech stuffed EFI 406 in progress
-=ICON Motorsports=-

 

congratulations and i wouldn't worry about the belt stretching issue. all the belts say to tighten them down, run the car for 5 minutes (drive it too) and then retighten the belt. that is what i did and never had another problem. get some pics man