I have been going through this for a year now, and I think I have just got it sorted.
Firstly I had a misalignment issue with one of the idlers in the Innovators West 8 rib kit (they now supply them with bushes to fix this), then I cracked the mounting hole for one of the idlers in the alternator bracket, then I had a faulty idler ... once I got everything aligned, I was still getting belt slap.
FYI, I am running a 10% OD and 3.5" pulley
Here's what I have learned:
In my case, this is not the belt on the tensioner going across and touching the belt on the idler ... It gets close, but doesn't quite touch. It is the tensioner running out of travel so the belt becomes loose on the low side of the engine and derails slightly ... then when the tensioner pulls tight again, one or two of the ribs are running off the pulleys, which shreds the edge of the belt.
Here's the fix.:
1. Removing the top idler will not make a difference ... if it adjusted all the way to the right, the tensioner does not not touch it anyway ... so why remove it and create less wrap-around on the blower pulley?
2. Use the Gates HD belt .. the standard ones stretch too much.
3. Use the shortest belt possible ... I had been using the K080962HD but I could not get the idlers tight enough so that the tensioner maintained enough travel, so I now have the K080952HD. This belt is perfect ... short enough that I have to loosen off the bolts on the idlers so they tilt and then force it onto the water pump.
4. Use a breaker bar and ratchet strap off the driver's side strut tower to pull the tensioner to its fully tightened position ... it should not even be touching the belt at this stage.
5. Get the ribbed idler below the tensioner as tight as you possibly can ... You can use something like a rubber handle of a hammer between the water pump pulley to push against the idler to tighten it (GENTLY) ... and make sure you use a piece of thick rubber or old serpentine belt over the pulley to protect the ribs.
6. Release and remove the ratchet strap, start the car, run it for a while ... the belt will stretch.
7. Replace and re-tighten the ratchet strap, and then re-tension the idler.
The tensioner should be as close to its far clockwise position as possible, with the right side bump stop approx 1/2" from the end and the other side having approx 1-3/4" of travel. That will mean that the tensioner has approx 80% of its travel to keep the belt tight.
I like the idea of the apposing tensioner, however if it runs out of travel in the opposite direction, it will just do exactly the same thing ... the belt will get loose and shred.
I hope this helps anyone who is having similar issues.
See the gap between the tensioner pulley and the idler pulley
This shows just how far clockwise that the tensioner is pulled ... with nearly 1-3/4" of circular travel before it runs out of movement.
