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Thread: PLUG GAP on blown sbc ??? please help

  1. #1
    Junior Member SHOW GUEST
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    PLUG GAP on blown sbc ??? please help

    Hi, thanks in advance for the help!! I have a 414 sbc 8-71 dbs blower and enderly mechanical fuel injection. base engine is 9.2 compression, blower 10% underdriven, running f&l sp-1 or sp-3 fuel, same as vp c12 c14. Ignition box is a 7-al3 not digital. My question is what should I run the NGK v-power #8 sparkplug gap at? I was told between .025 and .030..... is this close?? Reason I'm asking is, at the top end of the track I have what feels like a random misfire, engine has plenty of fuel -- went 20 #'s fatter on the pill, Have taken 8 degrees of timing out of it and still the same. Please point me in the right direction if you are familiar with this set up, THANKS!!!

  2. #2
    Senior Member RACING JUNKIE
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    I run around .040-045. on my blown sbc on gas or alky. what is the timing set at? Why are you not burning alky?

  3. #3
    Senior Member RACING JUNKIE THERATTLER's Avatar
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    on my blown alcohol sbc motor I run 25 thou on the plug gap with a 7 al3 , any wider and I have miss fire at high rpm , thats just what my set up likes,,,,Paul
    ***IN GOD WE TRUST***GOD BLESS AMERICA******

  4. #4
    You can and have tried larger but I will say .018-.025.
    Might check your pop off plate if you have coughed it previously.

    Dave Koehler
    http://www.koehlerinjection.com

  5. #5
    Senior Member RACING JUNKIE
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    miss

    You NEED to Ditch the MSD Box and get a GOOD Mallory Mag,Super Mag 3 0r 4 and you will be GOOD to go!!!
    Just talked to a freind in Indiana this Week same Problem,He Tryed the MSD Route?Took it out and went with a S/M 5 and its GREAT Now!
    Later
    G 8)

  6. #6
    Senior Member RACING JUNKIE
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    MSD works fine on blown carb or injected sbc and bbc's

  7. #7
    Administrator RACING JUNKIE bjuice's Avatar
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    .018 TO .020
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  8. #8
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    Quote Originally Posted by DaveKoehler
    You can and have tried larger but I will say .018-.025.
    Might check your pop off plate if you have coughed it previously.

    Dave Koehler
    http://www.koehlerinjection.com
    This is the voice of reason here, any time you increase pressure in the cylinder either with higher compression, NOS or forced induction you need to increase the intensity of the spark either by using a smaller gap or higher energy ignition. Smaller gaps are the easiest place to start.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
    __________

    Good work isn't cheap, and cheap work can't be good.

  9. #9
    Senior Member MASTER BUILDER
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    Ok it is learning time for me and I'm loving every minute of it. 434 sbc gas 15.33 to 1 compression and NGK #8's is 35 gap on the plugs ok or should it be tighter.
    Thanks Andy

  10. #10
    Senior Member RACING JUNKIE
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    Quote Originally Posted by jmarksdragster
    Quote Originally Posted by DaveKoehler
    You can and have tried larger but I will say .018-.025.
    Might check your pop off plate if you have coughed it previously.

    Dave Koehler
    http://www.koehlerinjection.com
    This is the voice of reason here, any time you increase pressure in the cylinder either with higher compression, NOS or forced induction you need to increase the intensity of the spark either by using a smaller gap or higher energy ignition. Smaller gaps are the easiest place to start.
    I have to agree 100% Mark.....Dave it sure is a blessing for someone of your stature to take the time to come on this site to give some advice. As for me its very much appreciated.


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