Supercharger belt fraying, unsure of cause or proper length to replace with

[pridemore54]

Hey guys hoping for a little education on a couple of questions. I'm gonna sound like a total noob but this is the first time I've even had to fool with belt before, let alone figuring out the length needs and dynamics of the belt and tensioner.

When I first picked the car up I noticed a couple frays at the front of the belt but wasn't overly worried. Within 200 miles and about 3 small pulls under boost, it now looks like this and was squealing during quick revs for downshifts.

Is there evidence here to diagnose why this is happening? Things to check for?

Setup details: Running a 2.9 Whipple with a 3.5in upper pulley with a metco 4# (8.60" dia.) lower. I believe this Metco Idler Kit with a 90mm idler and (3) 100mm idlers is what's currently installed. Going to verify that when I get home. Also worth mentioning, I have not experienced any belt slip so far.

My second question, what size belt should I order? The belt I pulled off is 82.75" length. I intend to get either a Gates green or RPM belt but have read about their vast differences and about adjusting the belt tensioner for them but have no clue what that entails. Anyone have guidance for me there?

 

[03' White Snake]

The belt tensioner does it for you. Key is to get the tab on the backside of the tensioner arm in the center of the cut out. Look at the back of the tensioner and you will see.

Remember, smooth pulley side to smooth belt side, and same for ribs. You will figure out how the belt goes. I flex tensioner first, put belt on that pulley, release. Run the belt over rest of pullies and do the supercharger last.

Dayco sells a pulley alignment tool to diagnose misaligned pullies. I just picked one up for $110. Not the easiest tool to use but works. It projects a laser onto the other pullies and you can find the misalignment. Then requires shims or grinding to fix.

I’ve been fighting belt issues the last yr and half.

 

[01yellercobra]

Get the alignment tool mentioned and check your lower pulley. Those and aftermarket alternators seem to be the main culprits in belt misalignment. It might be worth throwing a new tensioner on so you know what you're starting with.

I'd skip the green belt until you get the belt situation figured out. Spending $50+ on belts gets old quick.

 

[SVTdreamin04]

If nothing stands out by looking everything over and inspecting by hand, then check pulley alignment. Gates makes a laser alignment tool as well. I had issues with my belt walking as well. I ended up buying the gates laser alignment tool and quickly diagnosed my issue to be at the alternator bracket. It was causing the alternator pulley to be out of alignment by one full rib.


Sent from my iPhone using svtperformance.com

 

[pridemore54]

The belt tensioner does it for you. Key is to get the tab on the backside of the tensioner arm in the center of the cut out. Look at the back of the tensioner and you will see.

Remember, smooth pulley side to smooth belt side, and same for ribs. You will figure out how the belt goes. I flex tensioner first, put belt on that pulley, release. Run the belt over rest of pullies and do the supercharger last.

Dayco sells a pulley alignment tool to diagnose misaligned pullies. I just picked one up for $110. Not the easiest tool to use but works. It projects a laser onto the other pullies and you can find the misalignment. Then requires shims or grinding to fix.

I’ve been fighting belt issues the last yr and half.

Thanks for the info man. I'll have to look into what you mean by the tab on the back side into the cut out. Can't imagine there's anyway to look through that window without tearing the car apart.

Your method of installling the new belt is pretty much exactly what I intended to do. That or the alternator first cause getting the old one off that was an absolute pain.

I might run the same belt again and see if the same thing happens and also tracking how many miles it took for some more data.

 

[pridemore54]

Get the alignment tool mentioned and check your lower pulley. Those and aftermarket alternators seem to be the main culprits in belt misalignment. It might be worth throwing a new tensioner on so you know what you're starting with.

I'd skip the green belt until you get the belt situation figured out. Spending $50+ on belts gets old quick.

Not a bad idea on the new tensioner. I imagine they are not easy to replace while everything is still in the engine bay though.

 

[pridemore54]

If nothing stands out by looking everything over and inspecting by hand, then check pulley alignment. Gates makes a laser alignment tool as well. I had issues with my belt walking as well. I ended up buying the gates laser alignment tool and quickly diagnosed my issue to be at the alternator bracket. It was causing the alternator pulley to be out of alignment by one full rib.


Sent from my iPhone using svtperformance.com

Roger that. I'll likely grab the Gates or Dayton, whichever seems best, and go from there.

 

[01yellercobra]

The tensioner is easy to replace. Just make sure you get the one for the blower belt. I think the Lightning tensioner is the one a lot of people get.

 

[03' White Snake]

https://lmr.com/item/BT63/mustang-cobra-supercharger-belt-tensioner-03-04

Look at the tab in the images. You can see it in the engine bay without removing anything. It should be in the center of the opening.

 

[pridemore54]

https://lmr.com/item/BT63/mustang-cobra-supercharger-belt-tensioner-03-04

Look at the tab in the images. You can see it in the engine bay without removing anything. It should be in the center of the opening.

I see what you're saying now. Appreciate the help