Hello guys, I am getting the eaton pullied to a 2.80 and want to run an aux idler. Debating between a 90mm and 100mm, probably will go with the 100. My question was, is it ok to only run the aux idler and leave the rest stock? I have heard horror stories of these exploding but mainly at higher HP levels. If not, what belt size would be adequate with the metco 5 piece idler setup? would the stock belt fit fine with the 2.8 and 100mm only? I looked at the charts on the metco websote and it seems as if they should be pretty close but I wanted to see if anyone had experience with other belt sizes
Aux Idler Only?
- Thread starter SouthSideStang
- Start date
Yes you can run an aux idler and leave the others stock. Many people do this without issues. I was one of them. Like you stated, the problems seem to arise in more modified setups with larger crank pulleys and frequent upper RPM visits combined with hard shifts.
In addition to the added peace of mind, the 5-piece kit will allow you to gauge which aux pulley size to use (90 or 100) to maximize belt wrap around the blower pulley while maintaining adequate clearance. If I were you, I'd just do the 5-piece. Chances are you're going to end up doing it eventually anyway, they look pretty, and they're very easy to install. On top of that, the chart for belt length will be totally applicable assuming all your other pulleys are stock diameter (tensioner, alternator, crank...etc). The Gates RPM belt is the hot ticket these days while we're on the subject.
In addition to the added peace of mind, the 5-piece kit will allow you to gauge which aux pulley size to use (90 or 100) to maximize belt wrap around the blower pulley while maintaining adequate clearance. If I were you, I'd just do the 5-piece. Chances are you're going to end up doing it eventually anyway, they look pretty, and they're very easy to install. On top of that, the chart for belt length will be totally applicable assuming all your other pulleys are stock diameter (tensioner, alternator, crank...etc). The Gates RPM belt is the hot ticket these days while we're on the subject.
Thanks for the info, yeah I am really leaning toward the 5 piece from Metco, it does look nice and I would like the peace of mind. I have read great things about Gates RPM. Did you ever have to switch from just the idler to the other setup?
I wouldn't say there's a point where you necessarily have to upgrade all the idlers, but it just becomes more and more advisable as you put more stress on them. I.E. going to a larger crank pulley which is going to spin them faster. The tensioner is also known to be a weak point, but again the OEM unit is typically okay until you start changing out multiple pulley sizes and thusly using different belt lengths.
If you want, once I get home after work I can show you my pulley and tensioner setup along with the belt length.
If you want, once I get home after work I can show you my pulley and tensioner setup along with the belt length.
That would be great! Yeah I dont plan on going crazy with the setup, just a 2.8 upper and the aux everything else stock but I have read horror stories and I wanted to make sure I wasnt in the HP range where idler failure is common.
You'd be fine with just the aux. I ran stock idlers with a 3" blower pulley and a 2lb crank for a while without any issues. Granted I don't drive the car hard, but never a sign a problems.
I may even have my Billetflow aux idler sitting around somewhere if you want it. Can't remember if it's a 90 or 100mm, though.
I may even have my Billetflow aux idler sitting around somewhere if you want it. Can't remember if it's a 90 or 100mm, though.
Friend of mine ran the stock pullies with a 4lb lower for over 100k with no issues. Don't go crazy with belt tension and I think they'll last a while. But the Metcos do look good.
Thanks but unfortunately I already told the guy who's tuning it for me that he would order the parts. I wish i would have known this sooner 
Do you know if the stock belt size would work with only the upper and the idler? what was your experience?
Do you know if the stock belt size would work with only the upper and the idler? what was your experience?
You can grenade the stockers with just a small upper on the eaton. You probably will have better luck with just a lower swap....less tension needed....but with a tiny upper people are tempted to tighten the belt down to ridiculous levels searching for wrap, even mutilating the stop on the main tensioner arm. No-no. The metco duals are a great upgrade to get out of the way as a near first mod.
If you're hell bent not to upgrade all the idlers.....then at least go with the RPM belt since it requires considerably less tension than traditional belts to achieve wrap. Just easier on the components all the way around.
If you're hell bent not to upgrade all the idlers.....then at least go with the RPM belt since it requires considerably less tension than traditional belts to achieve wrap. Just easier on the components all the way around.
What size RPM belt would you recommend ? And I don’t mind upgrading all the idlers if it’s really needed with the upper only. I just want to make sure I get al the right parts. Belt size with the 5 piece metco ?
Do you absolutely have to replace the other stamped steel idlers?
No!
Are billet idlers better than the OEM stamped steel idlers?
Yes!
Is it a good idea to replace the OEM stamped steel idlers?
Yes!
Can I be left stranded if an OEM stamped steel idler explodes?
Yes!
For what the Metco billet idlers will cost you, I recommend that you spring for them and eliminate from your brain any worry about the stamped steel idlers exploding. It's not an absolute necessity, but it IS a good idea. And you get the side benefit of a matched set-up (upper pulley and auxiliary idler and other idlers). JMO.
No!
Are billet idlers better than the OEM stamped steel idlers?
Yes!
Is it a good idea to replace the OEM stamped steel idlers?
Yes!
Can I be left stranded if an OEM stamped steel idler explodes?
Yes!
For what the Metco billet idlers will cost you, I recommend that you spring for them and eliminate from your brain any worry about the stamped steel idlers exploding. It's not an absolute necessity, but it IS a good idea. And you get the side benefit of a matched set-up (upper pulley and auxiliary idler and other idlers). JMO.
Cobra bob thank you! What belt size would you recommend? I’ve only heard of your charts with sizes but can’t seem to find them. All the older threads have broken links
www.terminator-cobra.com under the Engine section
Thanks for this. Called LMR and they couldnt even tell me. AM told me to ask the forums. What do you guys think of this one?
Gates Green Stripe/FleetRunner Mustang 8 Rib - 75.13" Length (03-04) Cobra K080745HD
Not too far off the stock size.
I'll look through my pile of belts when I get home. At some point I was running a damn near identical setup to yours. Hopefully the numbers aren't worn off of it.
Thank you, I really appreciate it!
per Cobra Bob's guide, i think the belt i mentioned above (75.13) should work. Although his guide mentions one 92mm with 3 100mm calls for a 75.1 belt and the kit im getting has 1 90mm and 3 100mm, i think the difference in size can be adjusted at the tensioner?
This is the belt I was running with a 3” blower pulley and a 100mm aux idler. All other pulleys were stock. 76.75” if my research is correct. If I remember correctly, I suspected this one of slipping at WOT mid third gear and if I got into the throttle enough to break the tires loose, then let out it would chirp.
How it sits now. Zero OEM pulleys. Lots of wrap. Not a sign of slippage.
How it sits now. Zero OEM pulleys. Lots of wrap. Not a sign of slippage.
I really like the setup you have now. What size is that?
3” blower, 5-piece Metco, 2lb lower, J2fab alternator with 69mm pulley, and I wanna say the tensioner pulley is 73 or 76mm. Thump tensioner
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