Snub idler broke my pulley bridge and alt bracket!

[SLO_SHO]

Can't say I've seen, or heard of this before. Was facing some belt slip issues on my 2.6 pulley (2.65 vmp) with a gates green belt, so I went ahead and bought an rpm belt to see if that would help. Which it did the first time I took the car out, got full boost! That was about a week ago, than last night I took it out and was merging onto the highway, gave it a decent punch than BAM scared the hell out of me, my battery light came on and car was still running fine (no boost) so I knew it was something with the belt. Dogged it home, just as I was running out of battery I made it. Pop the hood and holy rats nest, the belt was completely shredded and wrapped around the supercharger pulley about 30 times. I then noticed my snub idler looked funny...took a closer look and the whole bracket to the idler snapped off of the pulley bridge and alt bracket behind it. One of the snub idler brackets also snapped. Just when I thought I had my belt slip figured out, something else happens funny how that works. I do not believe my belt was too tight, so I don't think I was stressing the pulley system too much. I did not install the snub idler, as previous owner did that. Maybe wasn't torqued properly? He did a fantastic job with the car so I feel like he wouldn't have missed that, however anything is possible. My one thought is maybe my belts before were too loose causing the bracket to weaken over time do to extra stress? Not sure if that would make sense.
Any ideas on what may have happened are welcomed, don't want to do it again.

Also, since that happened...does anyone have a pulley bridge and/or alternator relocation idler pulley bracket for sale?

Thanks. Will attach photos

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[01yellercobra]

Those RPM belts are supposed to be run a lot looser than stock. So if you were still set up the way you had the green belt that was probably your issue.

 

[SLO_SHO]

Those RPM belts are supposed to be run a lot looser than stock. So if you were still set up the way you had the green belt that was probably your issue.

When I had the green belt, I was getting tons of slippage I think because it was too loose, however I couldn't get the next size lower on to save my life. I went with same size belt, for HD and RPM. For the rpm belts I believe you want tension to be about 25-30% and that's where I felt it was. But, there a possibility I could have been wrong and had it too tight.
Sigh...expensive mistakes lol

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[01yellercobra]

Did you happen to see where the mark was sitting on the tensioner?

 

[SLO_SHO]

If I'm not mistaken, this was with same belt and idlers. Thump tensior

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[01yellercobra]

I'm pretty sure that's just a stop on the Thump stuff. The stocker has an alignment mark on the back to show where it's sitting in the travel.

Next time around I'd run a basic belt and go from there.

 

[SLO_SHO]

Yeah, that's the only pic I have on my phone, unfortunately. But from where it rests with no belt, that stop is about half inch to three quarters an inch over from resting spot. I do have some smaller idlers I could throw on to give it less tension. Or, like you said, I could go back to a different belt, which then I'll be fighting belt slip again.

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[CobraBob]

How old was the Gates Green belt? Was it the right size belt for your setup? If you have the right size belt with the right tensioner setting and a proper idler/pulley setup, you should not be fighting belt slip. I would go with a new Gates Green belt (correct size), ensure the tensioner is set correctly, and I would expect you won't see slippage.

 

[SLO_SHO]

How old was the Gates Green belt? Was it the right size belt for your setup? If you have the right size belt with the right tensioner setting and a proper idler/pulley setup, you should not be fighting belt slip. I would go with a new Gates Green belt (correct size), ensure the tensioner is set correctly, and I would expect you won't see slippage.

Appreciate the response. I bought two HD belts, which were brand new and were giving me slip. I tried getting the next size down on and couldn't for the life of me so I figured I had the tightest belt possible for my set up. It's stock crank pulley, one 90mm pulley, 3 100mm pulley (including snub) and 3.2 alternator pulley with 2.6 upper pulley. Have stock sized belt with that combo.

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[SLO_SHO]

Wondering if I could just get away with buying a new alternator idler pulley bracket and just jb weld the broken piece from the bridge. It appears the piece broken on the bridge is just a locating hole for the bolt that threads into the bracket behind the bridge. Would save me a few hundred bucks...but some others opinions wouldn't hurt.
Pic for reference of piece I would be jb welding back together.

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[01yellercobra]

You can try JB Weld. The worse that will happen is it'll break again.

I have an unpopular opinion about the green belts. They were made to run 100k miles in fleet trucks. So they're strong and stiff. As a result they don't grip very well. I'm not a complete hater as I have one on my truck. You'd be better off running a basic belt as it's more flexible and grips better in my experience. I'm running a basic Gates on my car with no problems.

I don't know that you'll never get away from belt slip completely with that small of a pulley. You'll probably need to get it coated to get enough grip. The down side is the coating will wear out the belts faster.

Going forward I would look into a bigger lower which will allow you to run a larger upper pulley. You'll get more belt wrap and it'll just be easier on parts. Since you need a new idler you might want to look into the Whipple aux idler as well.

 

[vr4]

You can try JB Weld. The worse that will happen is it'll break again.

I have an unpopular opinion about the green belts. They were made to run 100k miles in fleet trucks. So they're strong and stiff. As a result they don't grip very well. I'm not a complete hater as I have one on my truck. You'd be better off running a basic belt as it's more flexible and grips better in my experience. I'm running a basic Gates on my car with no problems.

I don't know that you'll never get away from belt slip completely with that small of a pulley. You'll probably need to get it coated to get enough grip. The down side is the coating will wear out the belts faster.

Going forward I would look into a bigger lower which will allow you to run a larger upper pulley. You'll get more belt wrap and it'll just be easier on parts. Since you need a new idler you might want to look into the Whipple aux idler as well.

I asked my buddy who is an engineer at Gates about them and he recommended against the green belts for the supercharger.

 

[03mach1torch]

I had a problem with belts melting on my Mach 1 with a cobra swap. 3.4 crusher. I couldn’t keep a belt on. Also over 30 lbs of boost. I broke my pulley bridge, tensioner and idler. I finally fixed the problem by going to a Whipple adjustable idler and American racing solutions tensioner. The Whipple idler bolts I didn’t feel were long enough so I ordered longer bolts from bolt depot.