upgrade question. pretty important and urgent. - Chevy Cobalt SS Forum : Chevrolet Cobalt SS Forums
 
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post #1 of 4 (permalink) Old 09-07-2010, 12:14 PM Thread Starter
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Location: riverside ca
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upgrade question. pretty important and urgent.

ok so im gtting a gm stage 2 kit but with a 2.9" pulley.. i have been told that if u run a 2.9" pulley you cant rev past 6600 or u can/will blow ur motor..ive seen many people running 2.9" pulleys and lower and seen race vids of them but i just want to know if thats true.. and if it is, is there something i can do to make that not happen? im getting a stage 2 and a trifecta tune. any help would be greatly appreciated! thanks..

EDIT: im getting it put on most likely wedesday.. which is tomorrow.. im also going to port the supercharger while its off.. im trying to be as safe as i can.. but once i heard that it got me kinda scared =/.. even though i still have 100k mile power train warrenty or 5 years.. if i blow my car up i guess im kinda covered...but just want to know what u guys think.. if its safe or not..

BLACK COBALT SS 2007:
3" ZZP HIGH FLOW CAT DOWNPIPE
3" MAGNOFLOW CAT BACK.
MEGAN RACING LOWERING SPRINGS APROX 1.25"
TINTED WINDOWS
3 10" SUBS
GM STAGE 2 CLUTCH
BRAND NEW TRANS
FEW LITTLE LOOKIN GOOD GOODIES

2.9" pulley
42lb injectors
gm stage 2 belt

SOON TO COME.
bigger HE exchanger/dual pass/drag radials or slicks. .
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post #2 of 4 (permalink) Old 09-07-2010, 01:54 PM
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i dont know why pulley size would matter in this case. i mean your valvetrain has limits but i would assume regardless of pulley size those limits are the same. a smaller pulley will just get you there faster. ive been told the stock valvetrain can go up to 7400rpms. but if your worried you can get upgarded valve springs from ZZP for under 200 bucks.
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post #3 of 4 (permalink) Old 09-07-2010, 04:02 PM
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Running a 2.9 pulley wont hurt if you at least have the gm stage kit tune. I had a 2.8 on mine and it ran fine all the way to the rev limiter which I believe was 7200-7400 I cant remember. Valve float will occur if you exceed 7400 rpm but the only way to do that is for someone to raise the rev limiter with a tune. I wouldnt go smaller then 2.8 without upgrading more things. really the weak point is the supercharger. just make sure when you get it tuned to make sure they leave a little room for adjustment and dont max out your injectors!!!

2009 Turbo Cobalt SS
traded in 2005 SS/SC

Dragracing is for fast cars, autocross is for fast drivers.


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This car looks fast even standing still!
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post #4 of 4 (permalink) Old 09-08-2010, 08:01 PM Thread Starter
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ok thnaks guys the guy had told me that a 2.9" pulley was maxing out the 42lb injectors,and if i reved to high i had the possiblity to lean out my motor and blow the pistons. im getting a custom tune from trifecta ive been told they know what there doing, so ill just make sure to mention not to max out my injectors.. and go with a mild/hard tune.. thanks for the help guys

BLACK COBALT SS 2007:
3" ZZP HIGH FLOW CAT DOWNPIPE
3" MAGNOFLOW CAT BACK.
MEGAN RACING LOWERING SPRINGS APROX 1.25"
TINTED WINDOWS
3 10" SUBS
GM STAGE 2 CLUTCH
BRAND NEW TRANS
FEW LITTLE LOOKIN GOOD GOODIES

2.9" pulley
42lb injectors
gm stage 2 belt

SOON TO COME.
bigger HE exchanger/dual pass/drag radials or slicks. .
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