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Help with spark plugs and blowout!!!

Discussion in 'SVT Shelby GT500' started by toennee, May 4, 2021 at 2:27 PM.

  1. toennee

    toennee Member Established Member

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    So I will try and make this short. I have an 08 with a ton or bolt-on's. 2.6 upper, 15% lower, professionally ported M121, 14 injectors and intercooler, twin 340 fuel pumps, JLT intake, long tube headers with hi flow cats, axle back, Roush intercooler tank, and I'm sure a few other things I cant think of.

    Since adding the 15% lower I have been battling spark blowout. Not sure how accurate the factory boost gauge is but it pegs hard at 15 hitting the stop.

    As far as the plugs go I was running SP471 starting at .30 and going down to .24. I was still getting blowout. Just replaced with TR6 started at .28 and was a little worse. Took them to .24 and its much better but still get some.

    Question should I take them down a little more, maybe .22 or go with BR7EF???

    Thanks in advance.
     
  2. DSG2003Mach1

    DSG2003Mach1 Premium Member Premium Member Established Member Single Barrel Sirs

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    how old are your coils?
     
  3. toennee

    toennee Member Established Member

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    I'm not sure, they are Ford coils and may be original. They car has 71,000 on it.
     
  4. me32

    me32 BEASTLY SHELBY GT500 TVS Moderator

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    TR6 are too hot for your setup. I would go with BR7EF at .28. If you still get blow out try .24 with BR7EF.
     
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  5. toennee

    toennee Member Established Member

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    That is what I was thinking. Thanks!
     
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  6. DSG2003Mach1

    DSG2003Mach1 Premium Member Premium Member Established Member Single Barrel Sirs

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    weak coils can definitely cause an issue. Age is more of an issue than mileage at this point.
     
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  7. toennee

    toennee Member Established Member

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    Update I put a set of BR7EF in at .28. They are better than the TR6 at .24 but still not prefect. As soon as the car cools off I'll gap them at .24 and see what happens.
     
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  8. me32

    me32 BEASTLY SHELBY GT500 TVS Moderator

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    Sounds like a start.
     
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  9. XP900

    XP900 Active Member Established Member

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    When I had issues I ordered a set of coils too - swapped them out to verify but they were not failing. My mileage was a lot lower but at 70K I wouldn't hesitate to order a set even as a test set.
    Are you getting OBD misfire codes on cylinders?

    I ran BR7EF gapped at 28 all the time and had to replace every 3-5K with a new set for misfires....common lifespan of those plugs in my 2010. I also ran the SP471 once or twice but never really liked them as much as the copper. They seemed to miss at idle. Never used Iridium due to all the negatives I read. My tuner asked why I was still using copper and wanted me to try iridiums for his tune. I installed and gapped at 30 -- TR7IX.

    I haven't felt any misses or rough idles with over 7K on these plugs and my boost was 19 max (hopefully I brought it down a little with recent exhaust changes).

    Try coils and then TR7IX at 30 if you can't resolve it.
     
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  10. VNMOUS1

    VNMOUS1 Well-Known Member Established Member

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    I run 024 at 26 psi. If you're having issues with BR7EF at 028 on your car it's not likely spark blowout. The coils last a long time but it's highly dependent upon your environment

    Sent from my SM-N975U using Tapatalk
     
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  11. SCGallo2

    SCGallo2 Balanced performance Premium Member Established Member

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    FWIW, I am at 19-20psi with NGK TR6s gapped at .028 and have never experienced spark plug blowout. In the past, I have experimented with NGK TR7-IX gapped at .028 and .025. The only difference between the three configurations is that I feel that the TR6s have better cold start and idle qualities when the engine is cold; once up to normal engine operating temp, I cannot tell the difference.

    XP900 asked if you were getting misfire codes. That would be useful information to share.

    Since your car started acting up after you installed the 15% lower, I would verify that the correct bolt and washer were installed and torqued properly. You would not be the first person experiencing random misfires from improperly installed balancer hardware.
     
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  12. toennee

    toennee Member Established Member

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    No missfire codes but im thinking I will just order a set of factory coils and see what happens.
     
  13. toennee

    toennee Member Established Member

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    So at .24 the misfire is almost gone but almost wont work so I'm going to order coils and hope that's the answer. Thanks everyone I will keep you posted. I am going on vacation next week so hopefully they get here before than.
     
  14. me32

    me32 BEASTLY SHELBY GT500 TVS Moderator

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    Keep us posted
     

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