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Thread: 434 Help

  1. #1

    434 Help

    I took my brand new 434 sbf to the track this weekend. The motor ran great on the dyno, it runs great and clean in the burnout box but it seems to struggle to pull past 5000 RPM, it eventually will but is not reving clean after that either. I pulled plugs and they looked pretty lean so I fattened it up a total of 6 steps and it didnt change it, I finally tried a new carb and that didnt change it either. I am thinking it is fuel pump now but wanted some other opinions. What do you think?

  2. #2
    Senior Member RACING JUNKIE curtisreed's Avatar
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    Have had a bad convertor do the exact thing you are describing.

    Curtis

  3. #3
    Senior Member DYNO OPERATOR
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    Aug 2005
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    [quote="doorracer"]Have had a bad convertor do the exact thing you are describing.

    Yep, me too. By any chance is your new 434 replacing one that blew up? That'll often damage a convertor.....
    Johnny

  4. #4
    I broke a rod on the old motor, i wouldnt say that it blew up though.

  5. #5
    The plugs never darkened up after the jet changes either, I hope it is not the connverter.

  6. #6
    Senior Member DYNO OPERATOR
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    That sudden stop of the engine when a rod breaks can damage the stator in the converter very easily. I've done it and seen others. Have you checked the stall? Is it the same as before? Should be higher if you're making more power. Will be much lower if the stator is broken. Does it sputter or just seem like it's laboring?
    Johnny

  7. #7
    It stalls fine, about 200-300rpm higher than the old motor, it labors to get past 5000rpm and then seems to sputter/surge. People watching the car say you can hear it in the sound of the motor.

  8. #8
    Senior Member MASTER BUILDER
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    What fuel pump, and how is it plumbed from cell to pump and pump to regulator?
    Unpredictable Pro Mudd Racing
    2009 MRA Pro Mod Champion
    3 time National Record Holder

    http://i251.photobucket.com/albums/g...mud/3158-1.jpg

  9. #9
    It is an Aeromotive A2000, # 10 to the regulator then #6 into a 2 into 1 to carb. It worked fine with my 408, the more I talk to people the more I am starting to think it may be converter. It just seems that with how much I fattened it up it should have run worse. I have 89 in front and 99 in back, the car should have been blubbering and burninn your eyes rich I would think but maybe not.

  10. #10
    Senior Member MASTER BUILDER
    Join Date
    Mar 2008
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    173

    fuel system problem?

    any chence there is a problem with any sort of obstruction in the fuel system. you may or may not have the right pressure and volume at top end. is there any sort of pressure guage you can see going through the traps just a thought art

  11. Racing Junk


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