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I believe my belt has stretched and it may be too loose, but I'm not completely sure how to read the gauge. There are definitely 3 lines there, but there may be a 4th as well, it's hard to tell. I'm not sure where the proper area for the notches to ride should be. One issue I had is that I ordered several belts when I was trying to find one, and one size was too small to fit and the very next size up seemed a bit too large. This is a stock truck engine and accessory system with the Holley Sanden 508 top mount system added.
So there definitely are 4 lines there? The reason I was suspicious is that the (from the orientation of the photo) 3 bottom lines are raised, cast into the body and the 4th line is completely flat, as though it could have been an incidental scrape. Was does the 2nd line from the bottom indicate?
After looking at some more tensioners I have found that there are only 3 markings on them. What appears to be a 4th marking is just a scuff mark on the body of the tensioner. Can anyone else comment on the photo above?
My shop manual for my 06 2500HD says the index rib should be between the outer ribs. Based on that, your belt is too long. I would try to get near the middle rib.
After about 8 trial/error belts from O'Reilly's -- mine ended up here. Seems to have been working flawlessly for 3 years or so. LS3, Corvette spacing, driving H2O pump, alt and PS pump. A/C low mount on its own belt behind the serp.
There are different size idler and ribbed pully wheels , sometimes putting on a slightly larger one will make a difference , from a guy whos has been in the same situation
I believe my belt has stretched and it may be too loose, but...
I’m curious why you think the belt is too long? Is it squealing? Throwing the belt? It’s also possible the tensioner has worn out and may need to be replaced.
I got the belt and from the start don't feel it was the correct size. I know now that the indicator is showing that the belt is too loose and the belt started chirping, then squeaking and now has a full time squeal as the belt has stretched.
After trying several belts the one that worked was one that had to be ordered. My setup is all truck accessories with the addition of the Holley passenger-side high mount brackets for a Sanden 508. The part# is Continental 4061125 (alternate Part# 6PK2857)
For anyone in the future reading this thread, my belt developed a pretty bad chirping that got worse and worse. The first problem was that the belt I had was too long, however that didn't solve the problem. After reading a lot of info online I found that putting a stainless steel washer on the bottom bolt of the tensioner helped get the belt riding in the correct position and so far it has solved the chirping belt noise.
For anyone in the future reading this thread, my belt developed a pretty bad chirping that got worse and worse. The first problem was that the belt I had was too long, however that didn't solve the problem. After reading a lot of info online I found that putting a stainless steel washer on the bottom bolt of the tensioner helped get the belt riding in the correct position and so far it has solved the chirping belt noise.
Great follow up info! Glad to hear you got it figured out.
This is the one that worked on mine. Truck accessories with Holley Sanden mount for Vintage Air
The pic below is one I took back in 2016 during the build, I don't have a decent picture of the tensioner indicator and it's not really visible now...
Sorry to bring this post back from the dead but I just installed the same setup. Holley 20-134 and 21-3, running a 145 amp alternator and have been trying to find a belt as well. Currently running a Gates K061140 and it is on the worn belt mark on tensioner instead of between the two small marks.
Sanden 508/sd709 compressor, Holley kit and all other stock accessories.
I tried to fit the K061130 but holy cow is it a tight fit, couldn't get it over the tensioner so returned it for the next size up. Going to attempt it again Thursday and putting it over water pump last and rotating engine to pull it on that pulley.
Just hoping you remembered if you had a bear of a time getting that belt on and if you are running the 145a alternator as well. Only other thing I can think of is going to a 76mm idler pulley right below alternator to give me little bit of extra slack I need to get the K061130 on.
Holley said to run the tighter belt, but with that 90mm pulley I am afraid its going to max out the tensioner and cause the belt to chirp/pop off.
With the K061140 it is slipping under hard throttle, same exact accessory setup as shown in your picture.
Last edited by Justin71105; Jul 16, 2024 at 05:53 PM.
It's been so long now I can't remember how the belt went on. I haven't changed it since 2019. I have a spreadsheet of every part number I used for the build, and the most updated info still shows the Continental # 4061125. The alternator was the stock alternator that came from the '04 Avalanche I used for the donor swap. Part# 601-00971.
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Tensioner Indicator 
