spark plug and gap recommendations

Discussion in 'PSI Superchargers Tech Questions' started by 3-D, Mar 19, 2009.

  1. 3-D

    3-D Member

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    I am doing blown alky for the first time. 540 BBC with conventional heads, 8-71 Superman blower, about 20-30% overdrive. What plugs do you guys recommend, and how much gap? I am running a MSD 7AL3, crank trigger and HVC II coil. Also do you think 30* timing is about the correct timing point to start? This is in a rear engine dragster. Also is there a need to ground something else since the block and the heads are aluminum? I grounded the starter bolt to the frame rail already.
    Thanks for any help.
     
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  2. Don Onimus

    Don Onimus New Member

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    Gap

    Not sure but after reading other posts, do you think the 7AL is enough for what you are doing? Just a thought.. Don
     
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  3. secondwindracing

    secondwindracing top alcohol

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  4. 3-D

    3-D Member

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    Msd

    I have seen many others run a 7AL-3 and decided I would try it before investing in a complete new system. This is still going to be a bracket car. Do you need to ground the heads without the mag?
     
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  5. blown400

    blown400 New Member

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    Ground CABLE from head to head and from the same point on head straight to battery. All grounds should go straight to battery never to chassis.
     
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  6. Dave Koehler

    Dave Koehler Member

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    Just ground the heads as stated and be done with it.
    .025
    You will need a killer battery and/or an alternator
    Starter on 24 volts
    You will likely need more overdrive

    Dave Koehler
    http://www.koehlerinjection.com
     
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    Last edited: Mar 19, 2009
  7. hemi altered 378

    hemi altered 378 Blown Altered

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    what if you don't run a battery? ground to chassis?
    Darren Russell
     
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  8. blown400

    blown400 New Member

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    As stated he is running msd 7 so thats why i said all grounds to battery. Just an opinion though.
     
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  9. MKR-588

    MKR-588 Member

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    You would think that static compression would have some bearing on his setup.
     
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  10. 3-D

    3-D Member

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    responses

    i have static compression at 12.3:1
    I run a "V" 16v battery
    There is a cable running from the grounding lug on the rear of the chassis to the ground on the battery, and the battery has a cable to another ground lug next to it.

    So .025 on the plug gap?
    any ideas on the plugs?

    Dave,
    I purchased your return system from you last week. That thing is sweet!!! How much overdrive do you expect to run. With the higher static compression, I thought it would be best to keep the overdrive down to be easier on parts. I am open to any info, and would like to hear the opinions from the experienced.

    Thanks
     
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  11. SoDak

    SoDak Active Member

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    We run a similiar setup but with SM IV's. My suggestion is to run more like .015" plug gap.
    As far as plug numbers, depends if your conventional heads have gasket or taper plug holes.
    R6061 or R5671 gasketed
    R5673 tapered

    I run -9's but it seems the rest of the world runs 10's.

    30° is a good (safe) starting point
     
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    Last edited: Mar 20, 2009
  12. iron468

    iron468 Member

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    i'm run 468 bbc 10-71 29% od with 7al gap .022 spark plug ngk 10 31'timing
     
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