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still under 400 hp

This is a discussion on still under 400 hp within the General Help forums, part of the LSx Technical Help Section category; hi i have strocker 408 im my chevy ingine with: 1.ls6 heads 2.long headrs 3.extream cam 4.bbk body thurtol 5.afe ...

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    still under 400 hp

    hi i have strocker 408 im my chevy ingine with:
    1.ls6 heads
    2.long headrs
    3.extream cam
    4.bbk body thurtol
    5.afe intake
    6.Gibson Super Truck Exhaust Systems
    7.LS6 intake manifold
    still i`m under 400 hp what should i do or are there anything rong with my setup

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    Quote Originally Posted by speeedo View Post
    hi i have strocker 408 im my chevy ingine with:
    1.ls6 heads
    2.long headrs
    3.extream cam
    4.bbk body thurtol
    5.afe intake
    6.Gibson Super Truck Exhaust Systems
    7.LS6 intake manifold
    still i`m under 400 hp what should i do or are there anything rong with my setup
    i can only assume u mean 400 rear wheel hp.........how about having it tuned?????? hard to read much of what u wrote but i would expect at least 430-450 rwhp with that setup

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    thanks for your fast replay put this after the tuned

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    Member stephen02ws6's Avatar
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    im not an engine builder or anything but it mught not be breathing that well. you got a cam for the 408 but heads and intake for a 346. better heads and a FAST intake should get you above 400. it all depends what the compression ratio is too. again im not an expert on this but thats what i think.

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    Quote Originally Posted by stephen02ws6 View Post
    im not an engine builder or anything but it mught not be breathing that well. you got a cam for the 408 but heads and intake for a 346. better heads and a FAST intake should get you above 400. it all depends what the compression ratio is too. again im not an expert on this but thats what i think.
    the compression ratio is 12:1 and i have zo6 heads and intake

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    Member stephen02ws6's Avatar
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    Quote Originally Posted by speeedo View Post
    the compression ratio is 12:1 and i have zo6 heads and intake
    ya but a 346 Z06. are they the base ls6 heads or are they ported and polished? just because they are from a Z06 doesnt mean they are the best or make the most power for your situation.

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    Very well said.
    I agree with Stephen


    300RWHP, 341RWTQ
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    Senior Member INMY01TA's Avatar
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    Quote Originally Posted by stephen02ws6 View Post
    ya but a 346 Z06. are they the base ls6 heads or are they ported and polished? just because they are from a Z06 doesnt mean they are the best or make the most power for your situation.
    Ditto. Cam specs as well? 1 7/8ths headers?

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    Slow'er'Ass Mr. Luos's Avatar
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    Cam specs are a must to understand what is going on.

    What transmission?



    You figure there are MANY 346's making over 400RWHP with stock LS1 heads...why wouldn't a 408 make at least that much with those parts?
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    Senior Member Orcus79's Avatar
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    I share the sentiment with those above, The engine is most likely being starved for fuel. The "stock" GM head are not built to flow a radacle cam. You need after market heads with some work done to achieve the needed flow rate.

    People see how much air the head flows, but what about how fast? velocity is just as important as CFM.

    Also what is you measured fuel pressure?

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    Senior Member Bottesini's Avatar
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    We also need to know what kind of dyno you are using a Mustang dyno will show much lower numbers.

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    I agree, this engine if properly tuned should be pushing 500hp. I suggest you try another pull on a different dyno.

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    what heads should i use ? the zo6 heads are i think 68cc should i use heads arounde 64cc ? i need sum cheap heads thats why i had the zo6

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    I agree with it being starved. It should be well above that 400hp mark.

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    what size fuel injectors and fuel pump???

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    Quote Originally Posted by speeedo View Post
    what heads should i use ? the zo6 heads are i think 68cc should i use heads arounde 64cc ? i need sum cheap heads thats why i had the zo6
    68cc and 64cc is the combustion chamber size. That really only effect your compression ratio. AFR recommends “Our 225cc intake runner cylinder head is ideal for normally aspirated 396C.I. to 427C.I.” Where stock LS6 heads are only have 210 cc intake runners. With that much displacement you are going to need larger intake runners and larger valves to let the engine breath properly then a stock LS6 Head can provide.
    Last edited by vetteemt; 10-13-2008 at 09:23 AM.
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    sum pepole adivce me to put the new ls3 heads its 63cc and 230 intake runner what you think guys ? they are kinda cheap and do the job
    Last edited by speeedo; 10-13-2008 at 12:04 PM.

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    Quote Originally Posted by Spaz View Post
    what size fuel injectors and fuel pump???
    20 and i`m going to 60 but i should tuned it and the fuel is stock should i chang it ?

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    O U 8 1 2 Spaz's Avatar
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    Quote Originally Posted by speeedo View Post
    20 and i`m going to 60 but i should tuned it and the fuel is stock should i chang it ?
    20lb injectors?! you'll need around 36 or so... could probably get away with 32... 60 is an over kill...

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    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by speeedo View Post
    20 and i`m going to 60 but i should tuned it and the fuel is stock should i chang it ?
    Yes.

    Your stock pump isn't good to much over 400HP.
    Injectors...should be 36-42 pounders.

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