Struggling at high rpm above 6000

Small Block Mopar Engine

  1. Bewy

    Bewy Well-Known Member

    Messages:
    1,528
    Likes Received:
    979
    Joined:
    Jan 1, 2021
    Location:
    Australia
    Local Time:
    5:41 AM
    Disconnect/disable the rev limiter. Loose timing chain &/or harmonics transmitted to the cam & then the dist can 'fool' the ign into thinking the rpm is higher than it actually is.
     
    • Like Like x 1
    • Thanks! Thanks! x 1
    • Oldmanmopar

      Oldmanmopar Going left turning right FABO Gold Member

      Messages:
      9,883
      Likes Received:
      7119
      Joined:
      Jan 8, 2009
      Location:
      Danielsville Pa. 18038
      Local Time:
      1:41 PM
      Everything on the motor is MSD
       
      • Like Like x 1
      • flyfish

        flyfish C8H18+N2O = :-D

        Messages:
        2,454
        Likes Received:
        1096
        Joined:
        Apr 16, 2007
        Location:
        Indy
        Local Time:
        1:41 PM
        I agree with PRH, try removing the nitrous plate and see if the problem goes away. It is possible you introduced a vacuum leak with the plate, or maybe one of your solenoids is leaking.
         
      • Jax

        Jax Well-Known Member

        Messages:
        208
        Likes Received:
        33
        Joined:
        Nov 6, 2009
        Local Time:
        2:41 PM
        It was an error... I am crossing the line @ 6300.... is where the miss firing is starting
         
      • Jax

        Jax Well-Known Member

        Messages:
        208
        Likes Received:
        33
        Joined:
        Nov 6, 2009
        Local Time:
        2:41 PM
        My compression is 10.5:1.... What is your suggestion?
         
      • Jax

        Jax Well-Known Member

        Messages:
        208
        Likes Received:
        33
        Joined:
        Nov 6, 2009
        Local Time:
        2:41 PM
        Yep, will remove everything, including the electrical section...
         
      • Jax

        Jax Well-Known Member

        Messages:
        208
        Likes Received:
        33
        Joined:
        Nov 6, 2009
        Local Time:
        2:41 PM
        Could you please elaborate? Didn't really get your point...
         
      • Ottmundr

        Ottmundr 68 Fastback

        Messages:
        8,158
        Likes Received:
        13478
        Joined:
        Oct 5, 2012
        Location:
        Sonoma
        Local Time:
        10:41 AM
        My first thought was valve float.
        And the OP needs a 383. :poke:
        Edit:
        Now is a great time to switch to a solid flat tappet cam, conical springs tool steel retainers, light weight edm lifters, light weight pushrods and ductile iron rockers. Lighten up the entire valvetrain and reduce the number of moving parts. Solid vs hydraulic, flat tappet vs roller, ductile iron vs roller tip.
         
        Last edited: Nov 9, 2021
      • Rat Bastid

        Rat Bastid .004 light

        Messages:
        922
        Likes Received:
        790
        Joined:
        Nov 23, 2020
        Location:
        22 The Avenue
        Local Time:
        10:41 AM

        My first suggestion is you shouldn’t need race fuel at that compression ratio. I know it sounds cool, but it isn’t needed. Did you measure the compression ratio or did you use the numbers provided on the piston box? Did you actually measure the chambers? If not, your compression ratio may not be what you think it is. I’m not saying this is your issue but it jumped out at me. As for plug heat range that 12 may be hot. You can try a 10 or even a 9 heat range and see what it looks like.
         
        • Like Like x 1
        • Rat Bastid

          Rat Bastid .004 light

          Messages:
          922
          Likes Received:
          790
          Joined:
          Nov 23, 2020
          Location:
          22 The Avenue
          Local Time:
          10:41 AM
          Also can you post all the cam numbers?
           
        • Jax

          Jax Well-Known Member

          Messages:
          208
          Likes Received:
          33
          Joined:
          Nov 6, 2009
          Local Time:
          2:41 PM

          upload_2021-11-8_16-7-19-png.png
           
        • Rat Bastid

          Rat Bastid .004 light

          Messages:
          922
          Likes Received:
          790
          Joined:
          Nov 23, 2020
          Location:
          22 The Avenue
          Local Time:
          10:41 AM
          That will run on pump gas and probably a 9 plug. See if you can find the thread RRR did on his /6 and read what he did to run pump gas. That’s a good thread.
           
          • Agree Agree x 1
          • Jax

            Jax Well-Known Member

            Messages:
            208
            Likes Received:
            33
            Joined:
            Nov 6, 2009
            Local Time:
            2:41 PM
            BTW As additional info......

            Besides adding the nitrous plate, we removed the distributor and intake to fix an oil leak we had..... Any suggestions that may arise from this process???
             
          • Oldschool

            Oldschool Well-Known Member

            Messages:
            429
            Likes Received:
            463
            Joined:
            Nov 2, 2005
            Location:
            Atlanta
            Local Time:
            1:41 PM
            I had the same issue in my 65 A-990 Hemi car back in the day. It took some trial and error with many things that have been mentioned in this thread. Nothing worked. 5500 rpm and it started misfiring. I spoke with Warren Barnett at Barnett Race Cars and he told me to upgrade the wiring to the MSD box and replace the battery with a fresh one. The MSD needs approximately 1 amp per 1000 rpm. The battery/wiring couldn't run the electronics on the car and supply the needed amperage for the MSD at higher rpm. I made that simple change and I have never looked back.
             
            • Like Like x 3
            • Thanks! Thanks! x 3
            • 1Badcolt

              1Badcolt Well-Known Member

              Messages:
              3,511
              Likes Received:
              2059
              Joined:
              Mar 15, 2013
              Location:
              Georgia
              Local Time:
              1:41 PM
              What brand distributor ???
               
            • Jax

              Jax Well-Known Member

              Messages:
              208
              Likes Received:
              33
              Joined:
              Nov 6, 2009
              Local Time:
              2:41 PM
            • dartindanno

              dartindanno Well-Known Member

              Messages:
              926
              Likes Received:
              1506
              Joined:
              Aug 25, 2011
              Location:
              Kenosha, WI
              Local Time:
              12:41 PM
              My brother chased that same issue for a couple months. I gave him an extra coil I had laying around and that solved the issue. Can't hurt to try
               
              • Agree Agree x 1
              • Jax

                Jax Well-Known Member

                Messages:
                208
                Likes Received:
                33
                Joined:
                Nov 6, 2009
                Local Time:
                2:41 PM
                Could total timing be a playing a roll here?
                 
              • roccodart440

                roccodart440 Well-Known Member

                Messages:
                6,052
                Likes Received:
                5060
                Joined:
                Apr 19, 2010
                Local Time:
                1:41 PM
                It could. Too much WOT timing can limit top end, not to mention, it's undesirable anyhow.
                 
              • Jax

                Jax Well-Known Member

                Messages:
                208
                Likes Received:
                33
                Joined:
                Nov 6, 2009
                Local Time:
                2:41 PM
                Right now, we have it set to 34 degrees total
                 
                • Like Like x 1
                1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
                  By continuing to use this site, you are consenting to our use of cookies.