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Another underdrive/harmonic balancer pulley question

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Old Oct 21, 2013 | 02:37 PM
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Originally Posted by UnVMySS
Do I have to use that hub and ac thing? Sorry im a newb on this but trying to learn.
2 pieces needed... Hub, and main pulley...
AC pulley is optional.
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Old Oct 21, 2013 | 02:56 PM
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What would the benefit of ac pulley be?
Do I use stock size belt? I am guessing so, just wanna be clear.

Last edited by UnVMySS; Oct 21, 2013 at 03:01 PM.
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Old Oct 21, 2013 | 03:16 PM
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Originally Posted by UnVMySS
What would the benefit of ac pulley be?
Do I use stock size belt? I am guessing so, just wanna be clear.

if you still have Air conditioning... you need the AC pulley (smaller 4 rib like stock)

and yes...stock length belt with a stock size damper
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Old Oct 22, 2013 | 11:23 PM
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Thanks. Browsing through sponsor sites, I came across a member by the name of 99blancoss who sold the ati 10% underdriven balancers for like 390 shipped. I went to his site and I don't see them at that price, so with that being said; which sponsor sells for the best price? Thanks!
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Old Oct 23, 2013 | 02:57 AM
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Summit has the ATI #917242 for $435


Free shipping
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Old Oct 23, 2013 | 04:46 PM
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Went with ati 10% underdrive from ws6 store for 410 shipped. Thanks guys. Mike at ws6store didnt know the belt number, but said he thinks it uses stock sized belts. Any takers on that?
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Old Oct 23, 2013 | 06:32 PM
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How come you didn't go with the full size ATI? Just wondering... if maybe there was a price difference or you just wanted 10% UD.
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Old Oct 23, 2013 | 06:50 PM
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Well, based off what you fellas said, I don't plan on going over 500 horsepower... So from what I understand, this will be more beneficial for my power goals. It was 419 bucks shipped. Ordered a grand worth of **** there as well.


Last edited by UnVMySS; Oct 23, 2013 at 06:56 PM.
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Old Oct 23, 2013 | 07:06 PM
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It's cool, the UD will be fine for your power level..


Ugh I hate looking at receipts! I just forked over $240 for a rear battery relocation kit...
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Old Oct 23, 2013 | 07:24 PM
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Tell me about it... Anyone know the belt number for this pulley? Mike at ws6store didnt know it...
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Old Oct 23, 2013 | 11:17 PM
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Originally Posted by UnVMySS
Tell me about it... Anyone know the belt number for this pulley? Mike at ws6store didnt know it...
if you cant find the number just buy a 1-2'' shorter belt from autozone and test fit it, you can always return it as long as you don't start your car and use it..

that's what I did, 2 trips to autozone.. finally nailed it dead on
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Old Oct 23, 2013 | 11:51 PM
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Cool Burken. You've been a lot of help man thanks.
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Old Oct 24, 2013 | 12:10 AM
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No problem!! Just make sure you spend over $20 to get your autozone rewards points! Lol
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Old Oct 24, 2013 | 06:59 AM
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Oh I do lol, even if I have to add a candy bar!
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Old Oct 24, 2013 | 11:26 PM
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Pity I didn't see this thread earlier....sometimes on E-Bay you can come across the ATI pulley you want at a way cheaper price, ATI sell off the blemished pulleys 'paint mark' at around 1/2 price.
Got mine that way
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Old Oct 25, 2013 | 10:58 AM
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Originally Posted by ls1 1990 VN
Pity I didn't see this thread earlier....sometimes on E-Bay you can come across the ATI pulley you want at a way cheaper price, ATI sell off the blemished pulleys 'paint mark' at around 1/2 price.
Got mine that way
Yea I've searched for the blem ones a lot, they never seem to have the one I want... But still a killer price 1/2 off
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Old Oct 25, 2013 | 11:59 AM
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I looked on ebay before hand. Ebay used to be the go to place for parts... Not so much anymore...
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Old Oct 25, 2013 | 04:16 PM
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Originally Posted by UnVMySS
I looked on ebay before hand. Ebay used to be the go to place for parts... Not so much anymore...
Yeah I cleaned up on eBay in the past. I found 10+ ls6 intakes at $75-$100, they were listed as ls1 intakes..

Those deals are still around if you know what to look for, but I try not to buy used stuff from people anymore.. I got burned twice this last year
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Old Nov 1, 2013 | 10:33 AM
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soundengineer, even though i dont see any proof im not going to dispute you if you say ATI is the best (nhra approved). what i will disagree with is implying its ATI or nothing. arent most if not all of these aftermarket pulleys sfi approved? doesnt that make them an upgrade over stock? do you have proof on rwhp gain from ATI over SLP or powerbond etc? im just the average backyard john doe hot rodder , why should i spend the extra $200 / $250 on an ATI? can you guarantee me my ls1 will last longer? top of the line parts arent for everybody. how much total have you spent on your hobby? how much could you sell it for? financially whats the best choice? thx just my one cent.
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Old Nov 1, 2013 | 11:20 AM
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Originally Posted by DANOZ28
soundengineer, even though i dont see any proof im not going to dispute you if you say ATI is the best (nhra approved). what i will disagree with is implying its ATI or nothing. arent most if not all of these aftermarket pulleys sfi approved? doesnt that make them an upgrade over stock? do you have proof on rwhp gain from ATI over SLP or powerbond etc? im just the average backyard john doe hot rodder , why should i spend the extra $200 / $250 on an ATI? can you guarantee me my ls1 will last longer? top of the line parts arent for everybody. how much total have you spent on your hobby? how much could you sell it for? financially whats the best choice? thx just my one cent.
actually..I can show proof from my own experience....
started with a stock pulley on a cammed motor.....went to an SLP and gained a couple of HP from the pulley change..

Later when I switched to my 408 I reused the SLP Underdrive Pulley.... when we went to the dyno my engine was falling off unusually early for the size of cam I have...
at the time it was a 248/252 on a 108 ICL...it was done by 6100 rpm and falling off quickly...quicker than expected by the cam builder and by myself.
from tuning hundreds and hundreds of cars I knew it should be more like 7000-7200 with that cam

we looked at everything...springs, valves, pushrods, lifters.....nothing made a difference...
I was stumped...but an engineer buddy of mine thought it may be harmonic vibration related.....being caused by the damper....or not being controlled by the damper
after a thorough discussion and talking to him about his racing experiences...I thought it was worth a shot and worth the piece of mind anyways since I was going to make more power with a power adder and I wanted to prepare for a dry sump or a vacuum pump anyways...
I bought a Full size ATI pulley/Hub combo with a Gilmer(HTD) belt drive on it to prepare for the vacuum pump

across the entire RPM Range(starting about 3000 rpm) I picked up 5-10 HP..... and my RPM carried out to 7400 rpm as expected...

all that issue(on my setup) was caused by an SLP underdrive pulley


so I gained power over the SLP Underdrive pulley by switching to the ATI, and I gained stability that allowed me to hold my power out to higher rpms.
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