KB 15lb Upper and 6lb Lower what belt?

stangin

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With a 3 1/4 upper 15lb KB pulley and a 6 lb Metco lower 3.5 alternater pulley, BF aux idler (90mm) what the heck size belt should I run? Any idea's?

Thanks
 

racerat

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I have a similar setup
3.5" upper
6lb (9") lower
3.5" alt
100mm idler

Belt is 81" and the tensioner indicator is dead center.
 

stangin

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Originally posted by racerat
I have a similar setup
3.5" upper
6lb (9") lower
3.5" alt
100mm idler

Belt is 81" and the tensioner indicator is dead center.

Ahhh, that should work then. I ordered the 6 lb lower today :) Where did you order the belt? Who would carry them?
 

mm49

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Gates Napa 25080810 it is 81 & 5/8 inches and fits tight but on mine does not slip.

Same pulley setup, but I am running two 100mm idlers with 90mm Metco idler. I have ran the same belt with stock idlers and Metco so it should work fine.

Jon L
 

racerat

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I'm running a Dayco belt from Advanced Auto....the only thing we could find in that size locally.
The belt is holding up great btw...no slip and no signs of wear after 2.5 months.

Part# 5080810
 

stangin

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Thanks guys.. and gals. I know the autoparts manager at Autozone here, he will order me whatever so I can try it, maybe a couple of sizes above and below just in case.
 

coleman

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racerat, how are you only seeing 15.6 psi w/ a 15# upper & 6# lower....:??:

i'm currently running at 11# upper w/ 6# lower & see 15#...

Originally posted by racerat
I have a similar setup
3.5" upper
6lb (9") lower
3.5" alt
100mm idler

Belt is 81" and the tensioner indicator is dead center.
 
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stangin

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Originally posted by coleman
racerat, how are you only seeing 15.6 psi w/ a 15# upper & 6# lower....:??:

i'm currently running at 11# upper w/ 6# lower & see 15#...


Actually this thought did cross my mind earlier tonight.. good question. I have the KB 15 lb 3 1/4" pulley and ordered the 6lb lower, guess I better go messure it to be sure now of what I have. I seem to remember posts a few months back that people that thought they got the 6 lb lower were shipped the 4 lb lower. Could this be the case, a low reading boost gauge or belt slippage?
 

mm49

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I have 3 1/4 upper with the new 6# lower (9.02") and see 21lbs total with no slip right up to 6200 rpm where I shift.

JL
 

racerat

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I've commented serveral times that I'm making less boost than I'm supposed to, but I am seeing the right amount of power.
The boost amount has been measured two ways...autometer gauge and autotap. It does the same thing on the dyno and on the street. It's been dynoed twice with the same combo with the same results.
I have a 3" exhaust so maybe it does breath a little better. Not sure.

Originally posted by coleman
but even a 3.5" upper & 9" lower should yield 17# according to Kenne Bell
I'm only off by 1.4# according to that chart.
 
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bassin247

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Originally posted by racerat
I've commented serveral times that I'm making less boost than I'm supposed to, but I am seeing the right amount of power.
The boost amount has been measured two ways...autometer gauge and autotap. It does the same thing on the dyno and on the street. It's been dynoed twice with the same combo with the same results.
I have a 3" exhaust so maybe it does breath a little better. Not sure.


I'm only off by 1.4# according to that chart.

That would be my guess.
 

coleman

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i've got the QMP 3" exhaust but stock manifold.

racerat, do you have headers?
 

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