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I have a 2004 Impala SS with the 3.8L supercharged V6. It has the stock 3.8" pulley. How small of a pulley can I go down to before needing an intercooler to avoid preignition? I am planning to get a cool air intake or a hood scoop. Also, what kind of power improvement can I expect to get with the new pulley (say a 2.8" vs. the 3.8")
 
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Be careful!!!!!!! If your changing the pulley your gonna change the speed in which the supercharger spins. You may exceed The maximum Rpm rating for that Supercharger and make it seize.
The Inter cooler itself will give you a horse power gain and Might give you a little extra gas mileage.
You don't want to seize up That super charger though!
Check with a tuner shop. They'll be able to tell you if I'm right or I just think I'm right.
 

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dont worry, that eaton can spin as fast as you can turn it with a stock lower pulley, and as small of a pulley as you want on the top.

if you are scared about detonation, get a water injection kit. otherwise, find someone who can program/dyno tune the car in your area after you install the pulley.
 

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Going down any pulley size, requires supporting mods no matter what or you will run into problems and cause knock in the engine. If say you wanted to go down to a 3.5 then you would need to have a good intake and exhaust set-up to start with. From that point on, the lower the pulley the more supporting mods.
 

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you cant go anylower that a 3.2" without cam or intercooler, you will have to much knock retard if you do and inturn you will crack a pistion, you wont hurt the superchager just your short block. i have the 3.2" on mine with cold air intake, computer, 1 heat range colder spark plugs, u-bend delete and cat back exhast. It runs great when its cold but if it gets to be 80+ degrees outside i can tell its to much i have major powerloss due to to much boost and inturn more heat in the motor that creates denation(knocking) so the computer retards the timing to elimate it, and retarding the time kills horsepower!!!

Jon
04 SS
65 SS Convert 396
 

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I have a 2004 Impala SS with the 3.8L supercharged V6. It has the stock 3.8" pulley. How small of a pulley can I go down to before needing an intercooler to avoid preignition? I am planning to get a cool air intake or a hood scoop. Also, what kind of power improvement can I expect to get with the new pulley (say a 2.8" vs. the 3.8")

I have a 04 Impala SS and I have a K&N cold air intake with exhaust, and I just put on a smaller pulley(3.4) I deff. notice a difference and my psi gauge that came with the car I max it out to 10PSI with ease! If you go any lower then a 3.4 you must do altercations to your car like getting the snouth of the sc machined and what not.
 

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to drp to a 2.8", theres alot that needs to be done, I would say the 3.ish rang would be safe, but find a used LS1M Scanner (or similar, they run about $100) so you can keep an eye on your *KR. I'm running a 3.4 right now, w. higher compression l36 block(.5:1 as opposed to a 8.5:1) and seeing a few degrees of knock (mostly tuning issues). Any thing under a 3.5 you will need a powerlog/PEMs/Headers, 180* T-Stat, tune and 1-2 ranger colder plugs. You wont nec. need to do a cam if you want to go further, yu can get a set of 90# LS1 Beehive(yellow) springs and 1.9 Rockers. once you go under a 3.4 pulley, you should prob look into either an Alky system or IC, hell even a SMALL NO2 shot (50) would help cool the intake charge enough to not need an IC. You'll prob get better performance out of the the Alky than the N02, and an intercooler than both.

Dont forget you will need a pcm whenever you start modding, if youre failiar w/ tuning, DHP offers excelent software for this ($500 new/$300-400 used).

With a 3.4 pulley (and supporting mods) you can expect runs around the low 13 range @ ~10xmph, depending on track/alt./temp/tires/driver/etc... IIRC, you're in the mid 14's now (stock).

your most restictive area of your exhaust is the downpipe & "U Bend". there are a few options to fix this, but a 3.6, dp, PEMS, 180* t-stat, plugs and tune should put you in the mid 13s
 

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If you go any lower then a 3.4 you must do altercations to your car like getting the snouth of the sc machined and what not.
IIRC, the smallest pulley you can run is 3.0 before machining the snout removing material from the EXTERIOR of the snout so the pulley fits

machined m90 snout
 

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I have a 2004 Impala SS with the 3.8L supercharged V6. It has the stock 3.8" pulley. How small of a pulley can I go down to before needing an intercooler to avoid preignition? I am planning to get a cool air intake or a hood scoop. Also, what kind of power improvement can I expect to get with the new pulley (say a 2.8" vs. the 3.8")


I just dropped my pulley on my 04 impala ss from a 3.8'' to a 3.4''. I put a new gator back belt. I only have a cold air intake and my car runs perfect. Doesn't over heat, my spark plugs are perfect and not getting too much heat. I don't think you need all that extra crap besides an air intake. So your will suck in more cold air so keep up with the smaller pulley. I wouldn't go any below a 3.4 without making serious changes in your vehicle. Let me know how it goes..
 

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I just dropped my pulley on my 04 impala ss from a 3.8'' to a 3.4''. I put a new gator back belt. I only have a cold air intake and my car runs perfect. Doesn't over heat, my spark plugs are perfect and not getting too much heat. I don't think you need all that extra crap besides an air intake. So your will suck in more cold air so keep up with the smaller pulley. I wouldn't go any below a 3.4 without making serious changes in your vehicle. Let me know how it goes..
Are you scanning your car to keep an eye on the *KR? That's the only real way to tell if it's a safe pulley drop or not. BTW, I have YET to see 2 of these cars, even if modded identically, act idecntically.
Also w/ a 3.4, i bet you're getting close to maxing out the stock injectors....
 

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Are you scanning your car to keep an eye on the *KR? That's the only real way to tell if it's a safe pulley drop or not. BTW, I have YET to see 2 of these cars, even if modded identically, act idecntically.
Also w/ a 3.4, i bet you're getting close to maxing out the stock injectors....
I am not scanning anything..tell me more of this, thanks
 

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With a 3.4 pulley (and supporting mods) you can expect runs around the low 13 range @ ~10xmph, depending on track/alt./temp/tires/driver/etc... IIRC, you're in the mid 14's now (stock).
NO WAY stock SS will run mid 14's, NO WAY......If that were true it would not take so much work to get them into the 13's! Best time I have got is a 14.86 @ 92ish mph with itake and u-bend delete and this car is way faster than stock, if you doubt me, someone honest take a stock car to the track and let us know.
 

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meant stock valve train, my bad, 3.4 pulley SHOULD put you into the 13s WITH SUPPORTING MODS. Depending on track conditions/driver i've seen cars run hi 14s on the stock 3.8, dont believe me? My buddy just turned a 15.2 on a STOCK (intake/exhaust only, NO TUNE) 97 GP GT (3.8 N/A), If i wasnt lined up next to him @ the track, i wouldnt have believed it. BTW he was on 18" Bullett rims + streettires, only weight reduction was removal of spare/jack/seats
 

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meant stock valve train, my bad, 3.4 pulley SHOULD put you into the 13s WITH SUPPORTING MODS. Depending on track conditions/driver i've seen cars run hi 14s on the stock 3.8, dont believe me? My buddy just turned a 15.2 on a STOCK (intake/exhaust only, NO TUNE) 97 GP GT (3.8 N/A), If i wasnt lined up next to him @ the track, i wouldnt have believed it. BTW he was on 18" Bullett rims + streettires, only weight reduction was removal of spare/jack/seats
My 14.86 was with no weight reduciton, had jack spare and all that! I ran a 14.99 with my 12" Solobaric in with all that other stuff!!! I couldn't get any traction, was running about 40psi in the tires, but I did a hella two gear burnout with NO water box! Next time out I aired down to 30psi and it made a heck of a difference in traction, if I could get my launch/reaction time down I am not sure what she would run. I think a blind person could get off the line quicker than me!! LOL
 

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OUCH!!! I bet your trans/axles loved that LOL!
If you have enough power and wheel speed you're fine. I have done several two gear smokies, some brake torqued others were just launching and the car shifted into second on it's own.


The first section of the burnout was first gear, pulled the car a little bit. Shifted into second and she set down and jumped to 6 grand. As it started chewing into the street the rpms started dropping a little. Dropped the e-brake, and she rode the burnout all the way!!!!!!!!!!!!






What can I say, she runs like a champ!
 

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Thanks for the advice!

Good thread...I've saved the information listed for my upcoming mods on my 04SS!

Looking forword to more mod info for the 04 supercharged 3.8...I plan on using the 3.4 pulley, a new performance exhaust, cold air intake and chipped/tuned professionally base upon my original thoughts and what I've learned here on this forum.

Just need the cash to do it at this point!
 

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IIRC, the stock SS exh is good for roughly 300HP, so from a performance outlook, the stock exh is still good thru a 3.4 pulley (i do recommend p-logs/PEMs/headers, and a downpipe though)

So unless you're looking specifically for sound, save the cat back for later and buy more go fast goodies;)

Also IMO don't waste your $ on press on pullies, grab a ZZP or Intense (the pulleys are interchangeable) MPS ;)
 

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Looking at about 10 horse power per .1 drop iirc. Make sure you have the supporting mods my friend has a gtp with the slp exhaust from the heads back, cool air intake, and some really nice plugs(cant remember where from atm) and he is still getting some KR with his 3.4 pully. He is about to drop to a 3.2 but he just bought an intercooler and will be doing some other mods first. Just remember when you get KR your computer is gonna pull engine timing and slow you down, not to mention possible damage.
 
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