Am i wasting my time with an idler?

I got a Metco 100mm dual BB idler and a 2.93 pulley laying around so my plan was to throw both on with the stock belt. The problem I'm running into is that the 100mm idler is a tight fit with the 3.1 and it's pissing me off. I want to try it with the 3.1 first to see if my MAF, pumps and injectors can handle it.

I googled the site and checked out CobraBob's page and the general consensus is that you don't need the idler with a 3" or larger pulley.

Does the 2.93 fit that criteria? It's close enough to 3" but I wanted to make sure. Maybe I don't need the idler and can run it without? Also, would the 90mm pulley be a better fit? instead of the 100mm on the aux idler? Maybe I could swap one of my engine idlers for the 100mm auxiliary idler.

No, you aren't wasting your time. Use the 100mm idler with the 2.93.

P49Y-CY said:

No, you aren't wasting your time. Use the 100mm idler with the 2.93.

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Thanks. I was trying to make it fit with the 3.1 but I don't see it working. The 3.1 brings the belt too close to each other.

I'll throw it on the 2.93 blower pulley and see how it fits.

I would see how much belt slip you have with just the 2.93( if you do)and see if you can remedy it with a 90 instead of a 100. The closer the idler gets to the blower pulley the hotter the blower snout gets.

As the belt bends over the blower pulley and then immediately bends in the opposite direction around the idler it creates heat(kind of like bending metal until it breaks). This transfers to the snout quickly.

Don’t believe me? Get a laser thermometer and check it after driving on both for a while.

Liquidsnake said:

I would see how much belt slip you have with just the 2.93( if you do)and see if you can remedy it with a 90 instead of a 100. The closer the idler gets to the blower pulley the hotter the blower snout gets.

As the belt bends over the blower pulley and then immediately bends in the opposite direction around the idler it creates heat(kind of like bending metal until it breaks). This transfers to the snout quickly.

Don’t believe me? Get a laser thermometer and check it after driving on both for a while.

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You make a very good point. I could see the increased bending causing additional friction which would translate to more heat. I could swap the 100 for a 90 to see the difference.

I run a 3.1 and 100mm. I put the snub idler on last. Hold the tensioner with a breaker bar and shove the belt over with the pulley until you get it on the bracket. Then put he bolt in.

apex svt said:

I run a 3.1 and 100mm. I put the snub idler on last. Hold the tensioner with a breaker bar and shove the belt over with the pulley until you get it on the bracket. Then put he bolt in.

View attachment 1598255

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apex svt is it possible that you have a different (or the early billetflow) version of the snub idler bracket?

here's a pic of my 2.93 billetflow pulley with 100mm idler, and it looks like i have much less space in between than you show in your pic.

I have a Metco idler and I didn’t like the fit with the 3.1. I felt it was too big. I also needed a longer belt, but what was bothering me, even with the longer belt, I felt that the 2 pulleys would have been too close and I was worried about increased friction or binding with the 3.1. At least with the 2.93, there is some space between the idler and the supercharger pulley.


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HPLouis said:

I got a Metco 100mm dual BB idler and a 2.93 pulley laying around so my plan was to throw both on with the stock belt.....I googled the site and checked out CobraBob's page and the general consensus is that you don't need the idler with a 3" or larger pulley.

Does the 2.93 fit that criteria? It's close enough to 3" but I wanted to make sure. Maybe I don't need the idler and can run it without? Also, would the 90mm pulley be a better fit? instead of the 100mm on the aux idler? Maybe I could swap one of my engine idlers for the 100mm auxiliary idler.

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I don't say on my site that a 100mm idler isn't needed with a 3.0" or larger upper pulley. What it says is "Adding an auxiliary idler is highly recommended with any pulley less than 3.00". Any pulley smaller than the factory pulley reduces belt wrap, so as you decrease the upper pulley size, the need for an auxiliary idler increases. Here's another related quote from my site. "To prevent interference, if you have a smaller upper supercharger pulley (ie. 2.90" or 2.76"), go with the kit that has a single 100mm (auxiliary) idler and three 90mm idler pullies." That is to address potential idler clearance issues.

What size are your other idlers? 90mm?

CobraBob said:

I don't say on my site that a 100mm idler isn't needed with a 3.0" or larger upper pulley. What it says is "Adding an auxiliary idler is highly recommended with any pulley less than 3.00". Any pulley smaller than the factory pulley reduces belt wrap, so as you decrease the upper pulley size, the need for an auxiliary idler increases. Here's another related quote from my site. "To prevent interference, if you have a smaller upper supercharger pulley (ie. 2.90" or 2.76"), go with the kit that has a single 100mm (auxiliary) idler and three 90mm idler pullies." That is to address potential idler clearance issues.

What size are your other idlers? 90mm?

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Yes, I followed your advice and got the three 90’s and single 100 and it fit.

About the 3” pulley, I wasn’t just quoting your site. I said that I checked your site and the one and the general consensus was that it wasn’t needs with a 3 or larger. I was checking your site and other and there was so many differing opinions, not from your site but from other sites, that I just went with your site and choose what I did, and it worked out.

Thanks again for the very informative site. It’s saved me several times over.


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Is it just me or do you change your pullies a lot? I'm not trying to talk trash, just seems like you're always playing with your pulley combos.

slo984now said:

Is it just me or do you change your pullies a lot? I'm not trying to talk trash, just seems like you're always playing with your pulley combos.

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You are correct. When I bought the car, the prior owner had a 2.76 on it. I datalogged the car and saw that I was close to maxing out the MAF (1004 AD counts), injectors (100% DC) and FP (98% DC) so I put it back to stock. Took off the intake, exhaust and everything. I wanted to get it back to stock to have a baseline. The car was also low on power (406rwhp and 466rwtq on the 2.76 with stock exhaust, intake and conservative tune). I started finding parts out on Facebook, eBay and the marketplace here and slowly started to put the mods back on the car, this time data logging everything. I also changed the alternator because the maxing out issues were due to low voltage (I datalogged 12.31).

I was on the 3.1 for a few months and, after data logging some more, I saw that I had enough room for a 2.93 so I added that. I didn't go back to the 2.76 because after some research and reading a lot of forums member's posts, I felt that the power increase is not worth the added stress, strain, RPMs and heat on the car. I saw a Metco aux idler for sale here, got that and after adding it, I saw the LFP pulleys wobbling so I had replaced those with Metco dual BB’s. I put the JLT back on after datalogging my IAT and IAT 2's and seeing that the temps go up at idle but drop back down quickly after the car starts moving so I was comfortable added that back. I replaced the off road pipe with a catted H pipe and found someone to trade my ATAKs for Stingers and now I'm here.


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You really need the whipple adjustable tensioner that allows you to slide the pulley into near infinite amount of spots along its mounting slot. This will allow you to accommodate multiple upper/lower pulley choices and in most cases.....use the same size belt! No more guessing, no more difficulty with installation.

Not only is it adjustable, but it also applies the pressure on the other side of the belt. According to whipple, that is the proper side to apply pressure. The typical snub is pressing on the outside and they claim that creates additional heat and will eventually cause premature snout failure.

It's a pricey piece, and a lot of times difficult to find.....but good grief is it worth it. Every penny.

c6zhombre said:

You really need the whipple adjustable tensioner that allows you to slide the pulley into near infinite amount of spots along its mounting slot. This will allow you to accommodate multiple upper/lower pulley choices and in most cases.....use the same size belt! No more guessing, no more difficulty with installation.

Not only is it adjustable, but it also applies the pressure on the other side of the belt. According to whipple, that is the proper side to apply pressure. The typical snub is pressing on the outside and they claim that creates additional heat and will eventually cause premature snout failure.

It's a pricey piece, and a loofa times difficult to find.....but good grief is it worth it. Every penny.

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I read about that. The availability is on/off but I've heard great things about it.

I emailed Whipple about my aux idler and they replied with the order form. I think I had it at my door in a couple days. But I'm sure being in the same state helped that situation. The only "downside" to it is that I couldn't route one of the fuel lines the way I wanted because there wasn't enough room behind the bracket. But's been nice to have with swapping the pullies around.

c6zhombre said:

You really need the whipple adjustable tensioner that allows you to slide the pulley into near infinite amount of spots along its mounting slot. This will allow you to accommodate multiple upper/lower pulley choices and in most cases.....use the same size belt! No more guessing, no more difficulty with installation.

Not only is it adjustable, but it also applies the pressure on the other side of the belt. According to whipple, that is the proper side to apply pressure. The typical snub is pressing on the outside and they claim that creates additional heat and will eventually cause premature snout failure.

It's a pricey piece, and a lot of times difficult to find.....but good grief is it worth it. Every penny.

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This.

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Thanks. I'm gonna give them a call. Like I said earlier, in my research, I heard nothing but great things about that tensioner.

Bdubbs said:

This.

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I had one of these on a car in the past and I THREW IT OUT, thinking it was some cheap tensioner. RIP

I'd go with the 2.93 and keep the 100.

2.93 and a 4lb lower was the sweet spot for me when I had the Eaton. It was a blast.

Should have kept them that way.. things were much simpler back then lol

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NateDogg said:

I'd go with the 2.93 and keep the 100.

2.93 and a 4lb lower was the sweet spot for me when I had the Eaton. It was a blast.

Should have kept them that way.. things were much simpler back then lol

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The grass is always greener...