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Thread: What octane 9.5:1 comp?

  1. 04-29-2013, 02:53 PM #1
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    miike
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    What octane 9.5:1 comp?

    Iron heads, forged internals 502.

    Thanks
    Top Gun 1992 22 Classic 540hp rebuilt HP500 King Cobra
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  2. 04-29-2013, 02:55 PM #2
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    BUIZILLA
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    minimum of 93...
    Charter Member - WAFNC, SBBR, KWOSG
    1955 Perfect Mate
    1986 Hornet III, 502-415 TRS

    www.donzi.org

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  3. 04-29-2013, 03:57 PM #3
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    Carb motor? Premium 93 or whatever you can get. Programable efi? You can probably run less octane.
    Jay Z.
    '93 White/Teal Classic 22
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  4. 04-29-2013, 04:05 PM #4
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    miike
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    Carb, no anti knock sensors
    Top Gun 1992 22 Classic 540hp rebuilt HP500 King Cobra
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  5. 04-29-2013, 07:13 PM #5
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    joseph m. hahnl
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    Depends when the intake valve closes.


    http://classicinlines.com/CompressionRatio.asp

    Not recommended
    Regular 87-89
    Supreme 89-91
    Premium 91-93
    Race Only
    below 7.0
    7.0-7.7
    7.7.0-8.4
    8.4-9.1
    above 9.1
    The ideal DCR range for a performance motor on pump gas is 7.5 to 8.5

    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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  6. 04-29-2013, 10:19 PM #6
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    roadtrip se
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    Running 93 with 10 to 1 on a MEFI3 system. Might be worth looking into aftermarket EFI...
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  7. 04-30-2013, 01:28 PM #7
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    pipnit
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    with those heads I would guess 93 or higher as people mention. Spend some $$$ on some aluminum heads and you can go a lot lower. I'm at 9.5:1 and run 87 octane with AFR heads and no problems what so ever. 87 is all I can find at the docks around me. At least it's not ethanol gas...
    DUNESMAN
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  8. 05-01-2013, 10:08 AM #8
    tmdog
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    9.7:1 with AFR alum. heads, 93 octane only.
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  9. 05-01-2013, 10:39 AM #9
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    miike
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    Sounds like I want 93 then...

    Don't want aluminum heads, I run salt with no FWC
    Top Gun 1992 22 Classic 540hp rebuilt HP500 King Cobra
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