MadScientist

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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whtsthislif4

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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PIMPALA-SS

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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1996 DCM #23,231

SSlowride

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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Gerry's 1994 Chevy Impala SS

65impSS

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

impala04ss

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.

04DetroitLS

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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04DetroitLS

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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impala04ss

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..

04DetroitLS

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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