Holley/Demon Carb stumble

Mopar Racers Forum

  1. PRH

    PRH Well-Known Member

    Messages:
    2,029
    Likes Received:
    3077
    Joined:
    Dec 14, 2018
    Location:
    So. Burlington, Vt
    Local Time:
    4:03 PM
    Well....... you coulda just slid a small drill bit into the hole and made sure it went in pretty deep :p
     
    • Like Like x 1
    • Cudafever

      Cudafever Well-Known Member

      Messages:
      4,106
      Likes Received:
      1427
      Joined:
      Sep 27, 2009
      Local Time:
      2:03 PM
      PRH wrote
      I don’t see any way that if both of those carbs were as sorted out as they could be...... that the PF bodied carb(with its smaller venturi) wouldn’t end up being the better choice for your application, especially at the elevation you race at.

      After tweaking the calibration my 850 MD worked pretty well....... but I really only used it on motors making over 600hp.



      Well it has been discussed...but not in this way.
      How about a little bit more thought as to why you think the Demon would work better at elevation.
       
      • Like Like x 1
      • PRH

        PRH Well-Known Member

        Messages:
        2,029
        Likes Received:
        3077
        Joined:
        Dec 14, 2018
        Location:
        So. Burlington, Vt
        Local Time:
        4:03 PM
        I rewrote that post, because I could tell it was going to be interpreted incorrectly.

        If you take out the middle of the sentence it’s clearer......

        “I don’t see any way that the PF bodied carb(with its smaller venturi) wouldn’t end up being the better choice”
         
      • Cudafever

        Cudafever Well-Known Member

        Messages:
        4,106
        Likes Received:
        1427
        Joined:
        Sep 27, 2009
        Local Time:
        2:03 PM
        Ok
        I have heard people say that a bigger carb is better in HIgh elevation is better because the air has no ram aka air pressure.
        Now i can jump on bored with both trends of thought.

        I thought you were going down that road.

        The hole reason i'm going down this road(besides not wanting a Demon spare parts box) is to see how it works. The Demon still has the best mph(but that was with 26 inch slick not the 28s i have on it now).
         
        • Like Like x 1
        • j par

          j par Well-hung Member

          Messages:
          22,860
          Likes Received:
          11488
          Joined:
          Jul 2, 2014
          Location:
          Portland Oregon
          Local Time:
          1:03 PM
          Maybe injecting some air...:D..
           
        • Cudafever

          Cudafever Well-Known Member

          Messages:
          4,106
          Likes Received:
          1427
          Joined:
          Sep 27, 2009
          Local Time:
          2:03 PM
          X X X X :lol:
           
          • Like Like x 1
          • j par

            j par Well-hung Member

            Messages:
            22,860
            Likes Received:
            11488
            Joined:
            Jul 2, 2014
            Location:
            Portland Oregon
            Local Time:
            1:03 PM
            You got to get on the juice train! LOL..:poke:...:D..
             
          • Cudafever

            Cudafever Well-Known Member

            Messages:
            4,106
            Likes Received:
            1427
            Joined:
            Sep 27, 2009
            Local Time:
            2:03 PM
            I will respond on your thread.
             
            • Like Like x 1
            • PRH

              PRH Well-Known Member

              Messages:
              2,029
              Likes Received:
              3077
              Joined:
              Dec 14, 2018
              Location:
              So. Burlington, Vt
              Local Time:
              4:03 PM
              It takes air flow thru the venturi and booster to create a pressure differential to get the fuel flowing.
              At elevation, the air is less dense, so it requires a larger volume of air to create the required differential.
              The smaller venturi speeds the air up and makes it more dense, which helps activate the main circuit earlier........ which should make tuning the bog out easier.......which should make it 60’ better.
               
              • Agree Agree x 2
              • Like Like x 1
              • j par

                j par Well-hung Member

                Messages:
                22,860
                Likes Received:
                11488
                Joined:
                Jul 2, 2014
                Location:
                Portland Oregon
                Local Time:
                1:03 PM
                I know when I go visit my son in Colorado everything boggs! I mean every car I hear everywhere coming off of stop lights make a big bogging noise..
                 
              • Cudafever

                Cudafever Well-Known Member

                Messages:
                4,106
                Likes Received:
                1427
                Joined:
                Sep 27, 2009
                Local Time:
                2:03 PM
                :eek::eek::eek:
                That's a low altitude-r Trying to breath up here.:D
                Like i have said before, it take a lot of work to make something N/A fast, up here.
                 
              • Cudafever

                Cudafever Well-Known Member

                Messages:
                4,106
                Likes Received:
                1427
                Joined:
                Sep 27, 2009
                Local Time:
                2:03 PM
                • Like Like x 1
                • Thanks! Thanks! x 1
                • mderoy340

                  mderoy340 Well-Known Member

                  Messages:
                  2,331
                  Likes Received:
                  1100
                  Joined:
                  Aug 2, 2012
                  Location:
                  Melbourne FL
                  Local Time:
                  4:03 PM
                  My AFR recently started going full rich 10:1 after the motor was up to temp during highway cruise. Turns out the mechanical pump was percolating and the fuel bowls were low. I'm changing to an electric pump with a return line. The ethanol in the gas today sucks.
                   
                  • Like Like x 1
                  • Agree Agree x 1
                  • Mattax

                    Mattax Just the facts, ma'am FABO Gold Member

                    Messages:
                    10,555
                    Likes Received:
                    6582
                    Joined:
                    Feb 7, 2013
                    Location:
                    Phila. Pa
                    Local Time:
                    4:03 PM
                    Could be the winter fuel. But low in the bowls should have been a slightly leaner mix if anything. Do you have a fuel pressure gage you can mount on the cowl?

                    I have one but don't usually leave it on the car. its not waterproof (and draws extra attention that not always a good thing)
                    It sits in this location.
                    upload_2020-4-16_22-28-35.png
                    The steel tubing gets held under the black backet atteched tothe the washer nozzle screw.
                    Red strap hold s the gage to the cowl.
                    AN-line goes to a tee in the carb feed. AN cap when not using the gage.
                     
                    Last edited: Apr 16, 2020
                  • mderoy340

                    mderoy340 Well-Known Member

                    Messages:
                    2,331
                    Likes Received:
                    1100
                    Joined:
                    Aug 2, 2012
                    Location:
                    Melbourne FL
                    Local Time:
                    4:03 PM
                    I have a SW gauge reading zero under the hood. I'm installing a low pressure fuel switch 4 psi with the new system. Turned on the electric pusher pump and motor recovered. It happened at idle after a local drive and I was able to see the empty bowls, low fuel pressure, and crappy idle. In FL there is no winter blend that I'm aware of.
                     
                  • Mattax

                    Mattax Just the facts, ma'am FABO Gold Member

                    Messages:
                    10,555
                    Likes Received:
                    6582
                    Joined:
                    Feb 7, 2013
                    Location:
                    Phila. Pa
                    Local Time:
                    4:03 PM
                    Meh. Looks like there is. At least that's inferred here.
                    US EPA approves Florida, North Carolina requests to change summer gasoline RVP | S&P Global Platts
                    Not surprising. It's cheaper to make and sell making consumers happy and more profit.
                    Many states have their own requirements, some including 'drivability' requirements. Bet Fla is not one of them.
                    previous (2013) map here Date of switch to summer-grade gasoline approaches - Today in Energy - U.S. Energy Information Administration (EIA)

                    Sounds like vapor lock on the suction side. Putting the line under pressure rather than suction should help alot.
                    When I've had that problem, it was also after idling and the worst was after stuck in traffic on interstate and a very warm spring day with winter blend.
                    I've added several layers of insulation and a shield to the lines back to the cross member. I also keep some 'storage fuel' on hand, which might happen to be in the gas tank when those conditions are present.

                    You prob won't need to do that with the pusher setup.
                     
                  • mderoy340

                    mderoy340 Well-Known Member

                    Messages:
                    2,331
                    Likes Received:
                    1100
                    Joined:
                    Aug 2, 2012
                    Location:
                    Melbourne FL
                    Local Time:
                    4:03 PM
                    Thanks for the info on the fuel. I also insulated the lines under the hood.
                     
                    • Thanks! Thanks! x 1
                    • Cudafever

                      Cudafever Well-Known Member

                      Messages:
                      4,106
                      Likes Received:
                      1427
                      Joined:
                      Sep 27, 2009
                      Local Time:
                      2:03 PM
                      Return fuel system back to the tank is the solution for vapor lock. electric or manual pump.
                      I had a little electric fuel pump that gave a pound or two to the machanical pump on the block.

                      When i went to a big electric pump with a return line off of the regulator. Vapor lock is a distant memory.
                       
                      • Like Like x 1
                      • Agree Agree x 1
                      • j par

                        j par Well-hung Member

                        Messages:
                        22,860
                        Likes Received:
                        11488
                        Joined:
                        Jul 2, 2014
                        Location:
                        Portland Oregon
                        Local Time:
                        1:03 PM
                        Vapor locked? What's that?..
                        You could get frostbite touching one of my carburetors...
                         
                      • Cudafever

                        Cudafever Well-Known Member

                        Messages:
                        4,106
                        Likes Received:
                        1427
                        Joined:
                        Sep 27, 2009
                        Local Time:
                        2:03 PM
                        Well the ProForm finaly got it fuel bowls today
                        IMG_2413.jpg IMG_2414.jpg
                        Which allowed me to put my Demon carb back together...............

                        The Demon dwarphs the ProForm in appearance
                        IMG_2419.jpg

                        Is this how you make a Dual Quad work?:p

                        Work day at the track tomorrow, then Mothers day.................probably will be next week before i can test it out.
                        Solder the hole up in the butterflies, in the demon carb that were to large anyways.
                        If necessary, i will drill a much smaller hole back into them. we will have to see............

                        need to set float level and pump arms, air cleaner bolt and throttle bolts so i can put the throttle cable on.(complete carb so easy carb swaps)
                        Will do a street test on both carbs...........then get a ET from Both of them at the track on the 18th.
                         
                        • Like Like x 2
                        • j par

                          j par Well-hung Member

                          Messages:
                          22,860
                          Likes Received:
                          11488
                          Joined:
                          Jul 2, 2014
                          Location:
                          Portland Oregon
                          Local Time:
                          1:03 PM
                          You rang for the Dual Quad Street demon Guru...
                          Screenshot_20200331-160025.png
                           
                        • Cudafever

                          Cudafever Well-Known Member

                          Messages:
                          4,106
                          Likes Received:
                          1427
                          Joined:
                          Sep 27, 2009
                          Local Time:
                          2:03 PM
                          Yeeeaaaahhh
                          How do i fit 2 carbs on a single manifold............one on top of the other?..... like a compound turbo?????????:wtf::lol:
                           
                          • Disagree Disagree x 1
                          • j par

                            j par Well-hung Member

                            Messages:
                            22,860
                            Likes Received:
                            11488
                            Joined:
                            Jul 2, 2014
                            Location:
                            Portland Oregon
                            Local Time:
                            1:03 PM
                            Screenshot_20200508-215516.png
                            Two carbs and three pedals..:thumbsup:...
                             
                            • Like Like x 1
                            • Disagree Disagree x 1
                            • 318willrun

                              318willrun Utube channel 318willrun

                              Messages:
                              14,515
                              Likes Received:
                              15189
                              Joined:
                              Sep 13, 2013
                              Location:
                              I'm here
                              Local Time:
                              3:03 PM
                              I like that pro form
                               
                              • Agree Agree x 2
                              • Cudafever

                                Cudafever Well-Known Member

                                Messages:
                                4,106
                                Likes Received:
                                1427
                                Joined:
                                Sep 27, 2009
                                Local Time:
                                2:03 PM
                                My car likes it tooo
                                But the Demon will get one last chance.
                                 
                              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.