I need help... supercharger belt.

I bought my car 2 months ago, previous owner bought from someone but didn't own it very long so he's not helpful.

Car is equipped with: 4 piece billetflow kit, 2.76 pulley. Metco lower pulley, guy listed it was "stock size". I measured the diameter and it was 8" from lip-lip.

The s/c belt had 1 rib shaved off, but drove fine no issue. The owner had a new continental gatorback belt, just never installed it, so I installed it saturday no problem (too easy). Belt size was 77.5.

45 minutes later on the way to a car show it destroys itself. Great, tow it back, do some reading, grab a gates 74.5 and 75in belt. NO SHOT.

Today, grab a 75.5 and 76 in belt... again, not a god damn shot. Me, my brother and my dad using all we got to get one of these on. Again, ain't happening. So I ran down to the store tonight and grabbed a dayco 77in. Got it around, pulled the aux idler off, pinched the belt together while my father bolted the idler back in. Super tight, perfect.

Get gas, all good, hitting 15.2lbs of boost. 3 houses down, belt rips.

There's no way I can get a shorter belt on. Maybe something just needs washers behind it? Misaligned? Man IDK what else to do. Tensioner bad? I don't wanna throw a thump tensioner on to have that not fix it.

I'll take some pictures tomorrow of the set up, maybe one of you guys see something that I'm not seeing.

If the belts shredding, it’s not a slipping issue, it’s an pulley alignment issue. Get a straight edge and check all the pulleys, including the alternator, and make sure everything is lined up. Something is off.


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^^ Agreed, something is out of alignment and the alternator is a common culprit.

I'll bet the lower pulley is out of alignment. Buddy of mine would slice off one rib religiously when he installed a new belt. We figured out it was the lower pulley, but he never bothered to fix it.

olympic said:

^^ Agreed, something is out of alignment and the alternator is a common culprit.

Click to expand...

Upon further inspection I think you are right. After doing a lot of reading I was basically only assuming it was gonna be the crank, but the tensioner/crank/blower all to the naked eye look good. Took a straight edge and yeah, if they're off it's negligible.

The alternator however looks to be slightly ahead of the lower idler and angled the the passenger side a few degrees. I ordered the gates laser tool so I'll double check with that, but I'm 99.99999% sure it's the alternator.

Great troubleshooting Lenny. You narrowed down the culprit pretty quickly. Let us know what you find out when you use the laser tool.

I had that problem when I put on a upr tensioner. Had to add washers to shim it out. Never had that problem since.

Their are so many unknowns related to the belt shredding. I had the same issue, mine would shred exactly 1 rib of the belt. i literally went through my entire system when i purchased my Cobra, and almost a year to figure it out, i actually though about selling mine I was so frustrated.

• replaced idlers to new double bearing
• replaced billet flow idler kit, with METCO kit
• replaced crank idler relocation kit with new kit just the brackets
• replaced really nice UPR billet tensioner with stock
• Shimmed alternator

*None of this corrected the problem!
After a year of growing pains and a few hundred bucks ($990.00 to be exact) my tuner had purchased an entire METCO 4lb lower crank pulley kit, for a terminator project he no longer had and did not need. He said he would like to try this new piece on mine no charge if it doesn't correct the problem. Long story short Installed it on my car and problem solved!

*Although he replaced the entire lower crank kit, The issue was actually my 4lb lower pulley it was about an 1/8 in wider in design than the new METCO 4lb pulley. I no longer have the pictures but seems like the previous owner installed a 4lb lower pulley brand unknown and it was off enough to make my belt jump 1 rib. This is something that is really hard to tell because the METCO pulleys are not branded/marked in any way. But it was a huge sigh of relief, Sorry for the long post just wanted to put this out.