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compression on new build

This is a discussion on compression on new build within the Internal Engine forums, part of the LSx Technical Help Section category; So i'm still in the beginning stages of my engine build for 2011, meaning still researching I suppose. I want ...

  1. #1
    Member egod's Avatar
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    Navy Blue Metallic
    1999 Trans Am

    compression on new build

    So i'm still in the beginning stages of my engine build for 2011, meaning still researching I suppose. I want to buy things in stages due to cash but want to have it all bought before i start assembly. I pretty much know what parts i think i am going with, as well as the intentions of the motor. However, I would still like some input as to a good compression ratio. Let me start with a few basics:

    1. LQ4/9 408 stroker
    2. N/A with n2o
    3. looking to make 500 N/A RWHP
    4. Street driven/ maybe daily

    I know there is a big difference in static compression and dynamic and I know the later is more important. So keeping in mind it will be street/DD the cam wont be very aggressive thus, dynamic should not differ to much from static. So what would anyone suggest for a good CR for a 500HP N/A motor with spray?

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    Member egod's Avatar
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    Navy Blue Metallic
    1999 Trans Am

    So...I was thinking 10.5:1 for pump gas is okay...anyone disagree?

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    SOM
    1998 T.A.

    11.2 11.3ish is fine for pump gas with these cars. I have seen guys run higher. Good quench is the key to running higher compression w/o predetonation. Optimum quench is .035-.040 for a pump gas LSx. Here is a calculator to help you figure out your setup>>>>>> http://www.rbracing-rsr.com/squishcalc1.html

  4. #4
    cutting and welding mark21742's Avatar
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    hugger orange
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    I'm running my 408 at 11:1 on 93 with no problems at all. 238/242 .595/.595 112lsa I do daily drive mine.

  5. #5
    Member egod's Avatar
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    does having a cam with a wider lsa make it tamer even with high lift and duration? it sounds like a can get a lot more out of the setup i was planning and still have a lot more streetability than anticipated

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    Impounded
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    gmcheviac

    wider lsa will be tamer and have a broader powerband

  7. #7
    cutting and welding mark21742's Avatar
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    hugger orange
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    Quote Originally Posted by egod View Post
    does having a cam with a wider lsa make it tamer even with high lift and duration? it sounds like a can get a lot more out of the setup i was planning and still have a lot more streetability than anticipated
    Yes it will be "tamer", but you will a get higher peak torque with a tighter lsa... A lot of time you spread your lsa farther than optimum to get a better, lower and more streetable idle

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