Thermoquad or Holley?

Fuel and Air Systems

  1. Mopar-Mitch

    Mopar-Mitch Well-Known Member

    Messages:
    1,408
    Likes Received:
    1396
    Joined:
    Jul 29, 2018
    Location:
    Kentucky
    Local Time:
    11:12 AM
    I have been having a lot of trouble out of my holley double pumper, since I bought the car last year. It has a oversized cam and I don't know any of the engine spec's. My intake is the old Torker 340 and the car needs a stall converter really if i keep running the current setup. I have no low end torque. I keep getting gas in the oil from the Holley its old and been rebuilt several times. A good buddy of mine gave me a New rebuilt from Chrysler thermoquad, it's for a 1977 400 HP engine. I can pick up a intake from another buddy, he has a stock 340 cast iron intake 71 casting he also has a wiand spread bore he'd sell me, I'm leaning toward the original cast iron because I can use the choke, what do y'all guys think, should I just buy a new holley or switch to a dual plane and use the thermoquad and maybe gain a little low end torque?

    00o0o_7NeGsIZdACT_600x450.jpg

    IMG_20190526_135002.jpg

    IMG_20190526_135432.jpg

    IMG_20190526_140124.jpg
     
  2. rumblefish360

    rumblefish360 So close, yet so far away

    Messages:
    35,589
    Likes Received:
    7495
    Joined:
    Jun 21, 2005
    Location:
    New York, on a Island
    Local Time:
    12:12 PM
    Mitch, I really like TQ’s. But I’d the cam is so big you need a high stall converter to keep it running & it came with a single plane intake, your probably going to like the Holley better. Knowing how big the cam is would be really good. You make it sound large. You may want to try a 4 corner idle 4150.

    The benefit you think you will have with the choke in the Thermoquad will probably not pan out.
     
    Last edited: May 26, 2019
    • Thanks! Thanks! x 1
    • Agree Agree x 1
    • brian6pac

      brian6pac Well-Known Member

      Messages:
      4,033
      Likes Received:
      2513
      Joined:
      Nov 15, 2016
      Location:
      N.E.Ohio
      Local Time:
      12:12 PM
      FYI that 9103 carb is off of a 77 400 HP, That being said I would go with the Holley.
       
      • Thanks! Thanks! x 1
      • Agree Agree x 1
      • RustyRatRod

        RustyRatRod 30 Degrees Outta Whack FABO Gold Member

        Messages:
        54,070
        Likes Received:
        22111
        Joined:
        Jun 7, 2010
        Location:
        Georgia
        Local Time:
        12:12 PM
        The problem with the TQ (or any metering rod carburetor) is that with a large camshaft the vacuum drops to the point that the metering rods "jump" and the idle mixture is very tough to get right. The Edelbrock style carburetors are "better" at combating this, but "I" have never been able to tune that out of a thermoquad. Maybe somebody else has and will chime in with the magic secret.
         
        • Like Like x 1
        • Thanks! Thanks! x 1
        • R4Sedan

          R4Sedan Life in the Fastback Lane FABO Gold Member

          Messages:
          4,197
          Likes Received:
          1359
          Joined:
          Nov 26, 2009
          Location:
          Tampa, Fl
          Local Time:
          12:12 PM
          Mitch I've always had luck with the Holley as well. Like Rumble said to bad you don't have the spec's off the cam so you could match up a converter.
           
          • Thanks! Thanks! x 1
          • Agree Agree x 1
          • 70aarcuda

            70aarcuda Master Hoader of SBM FABO Gold Member

            Messages:
            14,497
            Likes Received:
            2657
            Joined:
            Jan 16, 2005
            Location:
            las vegas
            Local Time:
            9:12 AM
            Hate to sound like a broken record...but a lot carb problems is not the carb...but ignition problem.

            Where is your timing at.....initial timing that is....big cams want a lot of initial timing....
             
            • Agree Agree x 2
            • Thanks! Thanks! x 1
            • Mopar-Mitch

              Mopar-Mitch Well-Known Member

              Messages:
              1,408
              Likes Received:
              1396
              Joined:
              Jul 29, 2018
              Location:
              Kentucky
              Local Time:
              11:12 AM
              Yep, I need to recheck the timing, the Holley keeps getting gas in the oil, float's seem to be right, it seems to be leaking off after I shut it down.
               
              • Agree Agree x 1
              • RustyRatRod

                RustyRatRod 30 Degrees Outta Whack FABO Gold Member

                Messages:
                54,070
                Likes Received:
                22111
                Joined:
                Jun 7, 2010
                Location:
                Georgia
                Local Time:
                12:12 PM
                It could be that it's running rich because it doesn't have enough initial. It's a very common issue. Good luck! If you were local, I'd say come help me put some sound deadener in and I'd tune on it for you....and have a few beers.
                 
                • Like Like x 4
                • Thanks! Thanks! x 1
                • Mopar-Mitch

                  Mopar-Mitch Well-Known Member

                  Messages:
                  1,408
                  Likes Received:
                  1396
                  Joined:
                  Jul 29, 2018
                  Location:
                  Kentucky
                  Local Time:
                  11:12 AM
                  Yep, now that sounds like my kind of a good time, sure wish I was closer!
                   
                  • Like Like x 2
                  • RustyRatRod

                    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

                    Messages:
                    54,070
                    Likes Received:
                    22111
                    Joined:
                    Jun 7, 2010
                    Location:
                    Georgia
                    Local Time:
                    12:12 PM
                    Me too!
                     
                    • Like Like x 2
                    • fishmens67

                      fishmens67 Well-Known Member

                      Messages:
                      6,014
                      Likes Received:
                      2915
                      Joined:
                      Nov 10, 2012
                      Location:
                      idaho
                      Local Time:
                      11:12 AM
                      I spent years trying to combat oscillating metering rods on Carters. The cure is switching to Holley.
                       
                      • Like Like x 3
                      • Agree Agree x 1
                      • Hellrats

                        Hellrats Still wrenching after all these years FABO Gold Member

                        Messages:
                        1,066
                        Likes Received:
                        795
                        Joined:
                        Jan 24, 2012
                        Location:
                        N.E. Ohio
                        Local Time:
                        12:12 PM
                        OK... I'll say it, change the cam :)
                         
                        • Like Like x 2
                        • B'cuda

                          B'cuda FABO Gold Member FABO Gold Member

                          Messages:
                          222
                          Likes Received:
                          179
                          Joined:
                          Feb 13, 2018
                          Location:
                          Newburg MD
                          Local Time:
                          12:12 PM
                          No expert here , wondering about the rest of the combo when you mentioned lack of low end torque . Rear end gear ratio etc. Are you sure about the size converter that's in there etc.
                           
                          • Like Like x 2
                          • AJ/FormS

                            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

                            Messages:
                            16,497
                            Likes Received:
                            5195
                            Joined:
                            Jan 19, 2014
                            Location:
                            South-Central Manitoba,Canada, 900ftelevation
                            Local Time:
                            11:12 AM
                            Holley floatvalves rarely leak. I'm guessing your PV is ruptured and gas is getting pulled back thru the vacuum circuit.. Pull the front bowl off carefully so as not to disturb the metering block. Then place a pan under the block and pop it off. If gas runs out from the cavity, there's your main problem. Put a 10.5 in there.
                             
                            • Like Like x 2
                            • brian6pac

                              brian6pac Well-Known Member

                              Messages:
                              4,033
                              Likes Received:
                              2513
                              Joined:
                              Nov 15, 2016
                              Location:
                              N.E.Ohio
                              Local Time:
                              12:12 PM
                              There is a hole in the base plate so there might not be fuel in the cavity.
                               
                              • Like Like x 2
                              • dartfreak75

                                dartfreak75 Restore it, Dont part it! FABO Gold Member

                                Messages:
                                5,356
                                Likes Received:
                                3542
                                Joined:
                                Aug 10, 2011
                                Location:
                                Virginia
                                Local Time:
                                12:12 PM
                                One thing to add that I dont see anyone else mentioning that thermoquad is a later carb most of them after 75 were lean burn carbs and dont have the port for the vacuum advance for the distributor. I don't see the port in the pic you posted I'm pretty sure that's a lean burn carb!
                                 
                                • Like Like x 2
                                • RustyRatRod

                                  RustyRatRod 30 Degrees Outta Whack FABO Gold Member

                                  Messages:
                                  54,070
                                  Likes Received:
                                  22111
                                  Joined:
                                  Jun 7, 2010
                                  Location:
                                  Georgia
                                  Local Time:
                                  12:12 PM
                                  You're probably right. Unfortunately.
                                   
                                  • Like Like x 1
                                  • AJ/FormS

                                    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

                                    Messages:
                                    16,497
                                    Likes Received:
                                    5195
                                    Joined:
                                    Jan 19, 2014
                                    Location:
                                    South-Central Manitoba,Canada, 900ftelevation
                                    Local Time:
                                    11:12 AM
                                    I'm pretty sure some fuel will remain in there at shut-down at least long enough for this test. I know for me it has.
                                    This would help explain the gas in the oil as well, as the float bowl is constantly draining.
                                     
                                    • Like Like x 1
                                    • RustyRatRod

                                      RustyRatRod 30 Degrees Outta Whack FABO Gold Member

                                      Messages:
                                      54,070
                                      Likes Received:
                                      22111
                                      Joined:
                                      Jun 7, 2010
                                      Location:
                                      Georgia
                                      Local Time:
                                      12:12 PM
                                      Actually, that's not quite correct. That port was never used for the distributor from the factory. It was used for the EGR valve. But you ARE correct in that it DOES make the perfect port for the distributor vacuum advance.
                                       
                                      • Like Like x 1
                                      • Thanks! Thanks! x 1
                                      • AJ/FormS

                                        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

                                        Messages:
                                        16,497
                                        Likes Received:
                                        5195
                                        Joined:
                                        Jan 19, 2014
                                        Location:
                                        South-Central Manitoba,Canada, 900ftelevation
                                        Local Time:
                                        11:12 AM
                                        That port is easy enough to add, and you can even customize the cut-in point.
                                         
                                        • Like Like x 1
                                        • Thanks! Thanks! x 1
                                        • Agree Agree x 1
                                        • Darter6

                                          Darter6 Well-Known Member

                                          Messages:
                                          3,911
                                          Likes Received:
                                          1062
                                          Joined:
                                          Jan 16, 2008
                                          Location:
                                          Nevada
                                          Local Time:
                                          9:12 AM
                                          My vote is for the Thermoquad. The TQ was free.Going to a dual plane will help bottom end torque with a automatic.Sounds like you can get the factory intake easy,and a 71 was the best TQ factory intake to have. I ran that set up on my Duster 340 with a 320* duration Crane cam. It idled at 1500 RPM. Granted my car was a 4 speed and had 5.13 gears But I would give it a try.You didn't say what gears you are running.
                                          Rusty,Help me out here ! I know you believe in the TQ's :drama::usflag:
                                           
                                          • Like Like x 1
                                          • Agree Agree x 1
                                          • abodyjoe

                                            abodyjoe Well-Known Member

                                            Messages:
                                            19,852
                                            Likes Received:
                                            4493
                                            Joined:
                                            May 22, 2004
                                            Location:
                                            Berlin,N.J. 08009
                                            Local Time:
                                            12:12 PM
                                            love the thermoquad but unless you get the tun right on it for your application its not really going to help you. a 77 440 was a smogger.

                                            i'd redo the holley on it and be done.
                                             
                                            • Like Like x 1
                                            • Agree Agree x 1
                                            • Mopar-Mitch

                                              Mopar-Mitch Well-Known Member

                                              Messages:
                                              1,408
                                              Likes Received:
                                              1396
                                              Joined:
                                              Jul 29, 2018
                                              Location:
                                              Kentucky
                                              Local Time:
                                              11:12 AM
                                              The rear end is a 1973 8 1/4 I don't know the ratio, its a sure grip but seems like awfully high gears, the whole drivetrain is from a 73 duster 340.
                                               
                                            • fishmens67

                                              fishmens67 Well-Known Member

                                              Messages:
                                              6,014
                                              Likes Received:
                                              2915
                                              Joined:
                                              Nov 10, 2012
                                              Location:
                                              idaho
                                              Local Time:
                                              11:12 AM
                                              I never used the TQ, but ran plenty of AFB'S and AVS's on many combos.
                                              Idling at 1500 rpm, tells me your TQ wasn't optimum on your combo.
                                              My vote is for the Holley and a dual plane. save the TQ as a collectable. and some headaches.
                                               
                                              • Like Like x 1
                                              • rumblefish360

                                                rumblefish360 So close, yet so far away

                                                Messages:
                                                35,589
                                                Likes Received:
                                                7495
                                                Joined:
                                                Jun 21, 2005
                                                Location:
                                                New York, on a Island
                                                Local Time:
                                                12:12 PM
                                                :rofl:
                                                :rofl:
                                                On a TQ, you remove the spring and allow the carbs internal cam do the work.
                                                 
                                                • Agree Agree x 2
                                                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.