KB 2.6, 2005 GT throwing belts, HELP!!!!!!

<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">Well, my car just threw its FOURTH belt. To say i'm completely frustrated is an understatment of the year. I have broken two different tensioners, and I've gone through 4 belts. None of the pulleys show any signs of misalignment. None are bent, and I can't find a single burr or dent or anything in any of the pulleys. What is the correct setup? What am I doing wrong!?!?!? I've heard this is a common problem on the S197s running the KB 2.6, so....what is the solution?????? I'm running a 4 and 1/16" pulley, making 7 psi, on an '05 mustang GT. I've been using the 1247 belt, all of which have broken. I tried one 1223, but that broke too. HELP!!!!!!!!!
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<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">How do I go about getting one from him? Just a PM, or what?

Is this the only reason I keep throwing belts? Just the tensioner?

Also, does anyone know where else i can get a 124.7 inch belt? I've been ordering them through KB, but i've heard some parts stores carry them in 8 rib and you can trim them? does Napa carry them?
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Yeah, shoot him a PM and ask him about it. From what I've read, the tensioner on the KB's is the main reason you throw belts. You can ask him more in depth questions, but I'm pretty sure a tensioner would solve all of your problems.

I wouldn't trim a belt, but that's just me. Try some local auto stores and see if they have them in 6 ribs. If not, find a place online.
 
Doing some searches, this seems like a common problem, and the solution is to get the "thumper tensioner" I talked to him, and he said the only other reason could be if they're out of alignment. He mentioned them being out of alignment by about 1 cog, and that is NOT the case on mine. I watched it idle for a long time, and as far as my eye can see, they're all perfectly aligned. How far un-aligned would they need to be for it to be a problem?
 
The tensioner was originally developed by thumprrr because he was breaking/bending the actual tensioner repeatedly. Just losing the belt was not the original reason for development. The tension failed and then the belt carnage would occur.

Make sure that your belt is free and clear of all obstacles when going around the pulleys, if it is shreading you have a problem with alignment or rub at high rpm. That wouldn't be a tensioner issue with that big old pulley on the car.

I do remember KB having an insert for an additional idler install that they supply in the kit. That added pulley cleared up a big rubbing issue on the driver side of the car. I'd start there, then have someone rev the car to 3500 or so RPM's while you watch the belt, make sure it travels clean.
 
<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">I have also broken two different tensioners. What happens is that the belt gets thrown, and its usually still in one continuous piece, but there will be like one or two feet section of it where two or three ribs tore off. I just ordered a thump_rrr tensioner, so lets see if that helps. I've watched it idle for a long time, and everything seems to clear just fine, there is plenty of room for it, and it doesn't look like it'll rub anything, even under load.
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IMG_3037.webp

this is with a 3.625 8lb pulley, supplied whipple belt and the 100mm ideler pulley
never once noticed any belt slip, belt looks great still, even tho i only have 300 miles on the supercharger
 
<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">ok, thanks. Thats a bit more travel than I have now. I'm gonna go ahead and move the idler thats next to the alternator down one more hole.
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