Considering 3.1"/4lb combo - thoughts?
- Thread starter KDog
- Start date
Do you have a ported blower? If so, I would consider a 6lb lower instead of the 4 with that upper.
KDog said:
you can be more aggressive than 4# with a 3.10 upper and be perfectly safe...the larger lower you use the more torque you will have which is good for these heavy cars...and gives you more surface for the belt to contact which helps with belt slip.
A 2.76 upper will result in a little over 15 lbs of boost in most applications, which is very close to what you'll get with a 3.10/4 lb combo. Not really worth the hassles and expense of switching out the lower if you can just change the upper pulley IMO.
Agree with Bandit, if you're going to go with a combo, go with 3.10/6 lb for 16+ lbs of boost.
Agree with Bandit, if you're going to go with a combo, go with 3.10/6 lb for 16+ lbs of boost.
unported eaton's remedy = 2.76KDog said:
Thanks for the replies. As Linn mentioned, I'm looking for the added torque (and hp) with less belt slip - thanks Linn. I know I could be more aggresive, maybe a 6lb'er, but I'd be happy with a 4lb lower...I think. ;-)
You don't get the extra torque from the lower pulley per se, you get it from spinning the blower faster which results in more boost. You will get the same amount of torque from a 2.76 as you will from a 3.10/4 lb lower combo.KDog said:
However, you are correct about the potential of less belt slip with the combo option.
+1 :rockon:LTHL VNM said:
IronTerp said:
Not so. You'll get more torque from a 6lb lower then you would a 2.76 upper. With combinations the right ratio for your blower is important. You'll also extend the torque band with a lower over an upper, and it hits much harder. To achieve your goal stay with 3.10 upper since you all ready have it, go with the 6lb lower and have minimal slippage with longer belt life. Now I will say this if you have a loose blower you may make to much heat with this combo. A heat exchanger is a must. I can dig up some sheets off the dyno to show you the difference on one car we did between the combos. Shoot me an e-mail if you would like to see them.
Rick :beer:
Blower rpm is blower rpm. A 2.76 upper pulley only Eaton will spin the blower rotors at 32.2% over the stock pulley configuration. A 3.10 upper/4 lb lower combo will spin the Eaton at 33.2% over stock......an insignificant difference. This is the combination that Kdag is referring to and that I was commenting on in my reply.
Now, a 3.10/6 lb combo will spin the Eaton at 41% over stock and this is a significant difference and will increase torque due to faster blower rpm! And thus why I suggested he go with this setup, if he wanted to do a combo :beer:
Now, a 3.10/6 lb combo will spin the Eaton at 41% over stock and this is a significant difference and will increase torque due to faster blower rpm! And thus why I suggested he go with this setup, if he wanted to do a combo :beer:
The only torque benefit gained by a lower is due to less belt slip. As IronTerp stated... blower RPM is blower RPM.
03soniccobra01
Banned
My 2.93 upper and 6lb lower work fine togather....No slip and tons of torque!
03soniccobra01 said:
What kind of numbers are you seeing with this combo? I presume you are ported correct?
I'm not a mechanical engineer, so I can't give a mechanics reason why, but from experience I've run better times with the 3.1/4lb combo than the 2.76 upper with my non-ported eaton. However it is cheaper just to put the 2.76 upper on, and come real close.
I do plan on having my blower ported this winter to get the full effects of my upper/lower combo.
I do plan on having my blower ported this winter to get the full effects of my upper/lower combo.
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sambandit said:
Im glad to hear you say that. That is what I am leaning towards now and probably will go with that when I get the port done.
What does one expect to see as far as boost levels go with a 3.1/6# combo? Stock manifolds and midpipe.
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This is a really good reference tool.
Your looking at 15.3 psi
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