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Do I need an underdrive crank pulley when running an EWP, no AC, or power steering?

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Old 06-19-2009, 05:09 PM
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Default Do I need an underdrive crank pulley when running an EWP, no AC, or power steering?
Just like the title says, is there any benefit of the pulley when you are only running one belt to the altenator??
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Old 06-19-2009, 08:10 PM
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Good question. I don't think there will be any performance gain since there are no other accessories to underdrive. But then again, I may be wrong. Hopefully someone else will chime in. Good luck.
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Old 06-19-2009, 10:19 PM
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I agree. I don't see anything to gain there.
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Old 06-20-2009, 01:38 PM
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Id also like to know.
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Old 06-20-2009, 02:16 PM
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I'm sure there is but a slight gain. Since a ud pulley is smaller than stock. And ud pullies are ussually sfi approved so that's a big plus.
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Old 06-20-2009, 11:52 PM
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Only thing I can think of is less rotational mass for the crank to turn.
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Old 06-21-2009, 12:48 AM
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Originally Posted by 383lt1impala
I'm sure there is but a slight gain. Since a ud pulley is smaller than stock. And ud pullies are ussually sfi approved so that's a big plus.
I agree with this. Being SFI approved is a big plus.
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Old 06-21-2009, 08:47 AM
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I have ud with just the alternator. don't know if it helps or not, but if it does, it ain't worth the money for the hp.
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Old 06-21-2009, 09:30 AM
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i run just the alternator, but i got one just for the sfi factor.
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Old 06-21-2009, 11:19 AM
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What belt do you guys run with the ud pulley and just the alternator?
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Old 06-21-2009, 11:50 AM
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Originally Posted by taws6m6
Only thing I can think of is less rotational mass for the crank to turn.
Isn't the ud pulleys a lot heavier than a stock one??
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Old 06-21-2009, 03:39 PM
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Originally Posted by cbra-klla
Isn't the ud pulleys a lot heavier than a stock one??
nowai! seriously, at least mine was considerably lighter then the cast iron lump of a stocker...

I'd say its worth it for sfi, weight reduction, and the .75 hp you might gain...
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Old 06-22-2009, 10:37 AM
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I already had my underdrive pulley when I decided to ditch all the accessories...I am running a 4 rib 31.5" belt with mine...





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Old 06-22-2009, 08:37 PM
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Thanks for posting that. Looks good. Could you not find a 6 rib?
Last edited by N20SS; 06-22-2009 at 08:48 PM.
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Old 06-23-2009, 07:19 AM
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I had the same question and ended up buying an ATI super damper with 10% underdrive. The ATI is probably one of the best and is sfi approved so I can't see it hurting anything.
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Old 06-23-2009, 09:31 AM
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Originally Posted by N20SS
Thanks for posting that. Looks good. Could you not find a 6 rib?
A couple places said they could order them but I was in a time crunch and ended up just going with the 4 rib...about 100 miles and 5 track passes and I've had no issues so far...
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