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Need advice!Engine bucks at 5000 rpm
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Thread: Need advice!Engine bucks at 5000 rpm

  1. #1
    Junior SCH Member
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    Exclamation Need advice!Engine bucks at 5000 rpm

    My 86 Gt was breaking down at around 5000 rpm with the stock injectors.I installed 30 lbs injectors and a mass air calibrated for the injectors.The fuel pressure is 80 psi at around 8 lbs of boost it still bucks and jerks at 5000 rpm.Would this be a fuel problem or ignition.I still have the stock ignition with a msd blaster coil ,motorsport wires and new plugs with a heat range colder.The dyno in my area the wide band o2 they used is not working.so i xcan,t really tell if it,s a rich or lean condition.Pulled plugs insulator is white tip is a greyish color.Any help would be appreciated would like to take itto the track this weekend. ....I have total advance timing set at 32 with thw boost retard at 1 Any advice would be appreciated...

  2. #2
    Senior SCH Member Chuck's Avatar
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    Be more discriptive of the bucking. Is it like you are hitting a rev limiter or does it just bog out and fall on its face?
    1993 notch, 357W forged pistons 9.2-1 comp,Vortech S-trim 3" / 8" pullies, AFR 185 heads, Trick Flow R intake, Anderson B451 cam, PMAS 80mm, 06 PMS, 60# injectors, 3.55 gears and PA SC C4, Dual Walbro fuel system. Best ET 10.35 @ 135mph

  3. #3
    SCH Moderator "SN Guru" speedytang's Avatar
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    Probably spark blowing out since you don't have a ignition box. Did you change your FMU disc for the 30lb injectors? What SparkPlug brand and Plug Number? Have more questions but this is a start.

  4. #4
    SCH Member
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    80PSI??????????? thats alot. With 16psi i run less then 60psi with 38's. Why are you pushing the 30's so hard?

    what are your plugs gapped at? I agree, you are probably blowing the spark out.
    94GT...Stock Block 306, Performer heads, RPM intake, F cam,
    V1 S-trim, AFM Powerpipe, 2.75" pulley, A9L, Interceptor 2, etc. :freaks:

    Darkhorse Racing
    89GT "The Killer Pumpkin"... 347, Victor Sr heads, Reichard Intake,
    F1-R, F.A.S.T, 160lb'ers, Glide, Reichard Intercooler, 25.5, etc. :evil:

  5. #5
    SCH Moderator RdRunnr's Avatar
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    What are the plugs gapped at? What's your timing? Are you running a btm?
    Eric

    1990 Mustang GT
    9.20 @151.18



    Check out this forum for AOD's/C4's: Click Click Racing Forums
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  6. #6
    Junior SCH Member
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    I'm Running ford plugs awsf 22 with 1 heat range lower than stock.gapped at 32.I am running a 8 to 1 disk .Will be changing to a 6 to 1 for the 30 lbs injectors.Was running the stock 19lbs witha 12 to 1 and was running over 100psi under full boost.But i am having the same symptom at aroud 5000 rpm with the 30 as the 19 , it jerks like it,s cutting out the rev limiter is 6200 so i am not hitting it.i have the timming set at 10 with the boost retard at 1. I am running 9.5 to 1 compression ratio ,Now i might thinks it,s a bit high for boost.might have to try a msd 6al.It works great until it,s starts to miss.Would like to get a low 12 this weekend ran 12.7 on the engine alone.Thanks guys **Also the msd boost retard as a a setting on the side with numbers on it.I have it set a 0 where should it be?

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