Holley 1920 diaphram return spring

Slant 6 Engines

  1. dennday67

    dennday67 Well-Known Member

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    I was getting near the end of a rebuild on my Holley 1920 list 3920 and noticed in the instructions a pump diaphram return spring. Mines missing it so i popped open my parts 1920 carb and its also missing it. I was wanting to know if a spring out of the Holley trick kit for the 4160/4150/2300 would work and if so what color. If not where can I get a replacement?
     
  2. slantsixdan

    slantsixdan =..=

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    There's no diaphragm return spring except on the '62-'63 1920s with round accelerator pump diaphragm stem. The '64-up units with flat stem have a drive spring but no return spring.
     
  3. cudamark

    cudamark Well-Known Member

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    PM me with your address and I'll mail you one.
    Thanks, Mark
     
  4. dennday67

    dennday67 Well-Known Member

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    No need for the spring as Dan said thx anyways cudamark
     
  5. desy500

    desy500 FABO Gold Member FABO Gold Member

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    P1070260.JPG

    I know this is an old thread , I have been reading as many as I can to learn about rebuilding these 1920's. So I didn't find the spring when I toke it apart , so I ordered the spring from Mike's , it is for a 1904 , but some where on his site he stated to another customer it was better to use it , then not have one? So I'm confused as to use it or not? P1070224.JPG I don't know what year this carb is from , or what it came on . I was having some stumble from a dead stop , and looking down the carbs with engine not running this carb was not squirting much fuel at all. After the rebuild , and putting the spring in it , now I don't see it squirting from that area at all , looks like fuel is only coming from the bottom section of the carb. Stumble is still there. I did not rebuild the metering block , I did spray all holes with cleaner , and air. The first photo - no fuel coming out of the slot on the left side , above the larger hole , fuel comes out of thin tubes on the bottom of carb .
     
  6. slantsixdan

    slantsixdan =..=

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    That is a Holley 1920 for a 1968 225/automatic.

    You should see solid shot of fuel squirting towards the middle from a hole in the inner wall of the carburetor, each and every time you operate the throttle lever with the engine off. If you do not, the accelerator pump has a problem. Not assembled correctly, missing parts, check balls not sealing. A faulty accelerator pump means you will get a stumble from a dead stop.
     
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    • desy500

      desy500 FABO Gold Member FABO Gold Member

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      THANKS again for the info , I will take it apart again.
       
    • desy500

      desy500 FABO Gold Member FABO Gold Member

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    • slantsixdan

      slantsixdan =..=

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      That's a '69 225/automatic. It'll probably have provisions for the throttle plate anti-ice system, which is a bit of a nuisance to deal with properly if your air cleaner isn't also equipped.
       
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      • desy500

        desy500 FABO Gold Member FABO Gold Member

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        As always THANKS for the good info
         
      • Killer6

        Killer6 Well-Known Member

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        Keep us updated, I may have 3 or 4 of those carbs around here I can dig up when the weather gets "springy" again, if You need one still let us know.
         
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        • desy500

          desy500 FABO Gold Member FABO Gold Member

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          any issues with keeping the threaded fitting on the passenger side of the carburetor base for the anti - ice system plugged? have headers and none original air cleaners
           
        • slantsixdan

          slantsixdan =..=

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          You can probably make the car run OK, but it'll screw up the idle calibration somewhat.
           
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          • desy500

            desy500 FABO Gold Member FABO Gold Member

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            Did you find any 1920's laying around? I am looking for another , looks like the 3920 I rebuild for the back is working good , ( no return spring on that model ) but the front one - with that anti ice system is in pretty bad shape all pitted inside , and one of the metering block screws broke off when I was taking it apart. Was using a small screw driver , and it broke easily. I think I read somewhere that you should not remove the throttle plate and shaft assembly because they like to leak when disturbed , anyone have any comments about that? I will need to alter the linkage to match up to a different carb because of the way they sit on the Offy intake.
             
          • Killer6

            Killer6 Well-Known Member

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            I'm sure I have some, I'll look this weekend, if I can find a matching list# to Your good one I'll see what condition it is in. As far as removing throttle screws, blades, & shafts
            are concerned, I've done it, but it isn't necessary for a good rebuild. I've done it to modify carbs, but never to rebuild them, if there is some pressing reason You feel it is needed
            I will list some tips for You to do so successfully.
            Edit; Only if the shaft bushings/seals(if equipped) need replaced would You want to
            take the throttles apart for a rebuild.........................
             
          • Killer6

            Killer6 Well-Known Member

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            Well, so far I've found (3)BBD's, (4)BBS's, & (1)1920, and it's not a match to Yours...............but here are the numbers.........
            6594 1373
            3698347
            it has an external bowl vent tube for canister equipped vehicles. I've had at least the one from My '69 Dart, the one from a '70 Valiant 4dr. I parted out, the one from My
            '72 Swinger that got the built six from the '69, & the one currently on the '72 Duster. Plus I believe the orig. set-up from another eng. project I purchased from somebody
            w/a header etc.. crap.....I'll check the one on the Duster after work tomorrow. I'm known for not throwing away anything pretty much, but for now..............:rolleyes:.......
            UPDATE;
            OK, the one on the Duster looks just like the other on equip/feature wise, but is a
            different list#....................
            7585
            0152
             
            Last edited: Apr 24, 2017
          • desy500

            desy500 FABO Gold Member FABO Gold Member

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            Do you think it is important that both carbs are the same number , or that they are both 1920's ? I picked up a second 3920 a few weeks back from another member , and rebuilt it , but before I asked about the throttle shaft I had already removed it to make changes so it would connect to my linkage , now have a very small leak. That 's why I was looking for another.
             
          • slantsixdan

            slantsixdan =..=

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            Yes, if you want the twin-carb setup to run well, the carbs need to be matched -- not just the same jet number, but identically matched carbs in equal and excellent condition. A pair of new and matched 1945s are going to be a lot easier to find, and do a lot better for you, than trying in probable vain to cobble up two worn out 1920s or BBSs.
             
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            • Killer6

              Killer6 Well-Known Member

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              First up, Yes it is most desirable to have two (or however many) identical carbs for multiple carburetion. There can be many differences in the same basic model carb that
              have a large influence on the way it meters & delivers fuel, idle/main jets to idle/main air bleeds combined with emulsion bleed count/size/height(or lack of), design manifold/
              base running temp calibration,high altitude/Cali/fed calibration, variations in power enrichment to main ratios, vacuum only vs vac/manual power enrichment, accel discharge
              rate, volume, & timing,...transfer slot/port calibrations........etc...etc..........even two identical carbs have to be timed in sync to function optimally.....My '66 Yamaha YL1 has
              a cool little 2 cyl. 2 stroke 100cc twin,...I can feel almost immediately when the cables let the throttle slides get a tiny bit out of sync.,..You can hear and feel it!
              So back to Your second 3920, where exactly is the air leak,...around the shaft at the throttle body or...???
               
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              • desy500

                desy500 FABO Gold Member FABO Gold Member

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                Well , that was a lot to swallow, thanks for typing it out. After running with both rebuilt 3920's it was the best it has ran since I got her , but the linkage was not pulling all the was back to idle , it would pull back to about 1/8 away from where idle screw should rest , and then slowly slow down to rest . so with engine off I tried to trouble shoot why - looking at the linkage of both carbs , the springs , everything looked like the pixs I took when I disassembled ? So I disconnected the linkage from the second 3920 ( front ) and the back carb worked correctly ( returning to ideal every time) Anyhow continuing to look for the cause of the hang up on front carb I notice a small amount of gas from the shaft where it comes through on the side where the linkage connects. don't see anything if engine is running , at idle, and not moving throttle , but with continued moving of throttle small amount of gas will appear . I will get a pix and post it
                 
                Last edited: Apr 25, 2017
              • desy500

                desy500 FABO Gold Member FABO Gold Member

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                #1 is matching 3920's
                2 is front before pumping throttle
                3 is after 10 pumps - a little wet
                4 is after 15 pumps - about 2 drops fell on towel
                engine was not started today , no gas leaked out over night - engine was ran yesterday

                carbs_20170425.jpg

                front 3920 4.25.17.jpg

                10pumps wet.jpg

                15pumps 2 drops.jpg
                 
              • Killer6

                Killer6 Well-Known Member

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                It may just be the pic, but to My eye, that frt. linkage rod is angled, maybe the end at the frt. carb goes in from the frt. instead of from behind. That may be causing a bind if so.
                Ahhh, well, You took the shaft out & cleaned everything nicely, now fuel that hits & sits on the throttle/shaft leaks every time the pump squirts enough. It is what it is now w/o
                restoring the holes in the throttle base, but shouldn't really affect the running of the car much, just don't pump the gas if You're not planning on starting it!! As I stated above,
                check the throttle positions in relation to each other, and slowly operate the carbs watching the timing of the accel. pump arms, they should be as in unison as possible. If You
                need to do a lot of adjusting for a baseline, turn off the fuel/pinch the hose & run the carbs out of fuel,..pumping the whole way so they're empty before You begin.
                 
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                • desy500

                  desy500 FABO Gold Member FABO Gold Member

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                  Ya , I think that is what I'm going to do , maybe some day I will go back to 1 carb. maybe a 2 barrel? Is it a big deal to put a bushing in there if the leak gets worse?
                   
                • Killer6

                  Killer6 Well-Known Member

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                  Bushing the throttle body is best left to somebody w/the right tools & experience, but it can be done at home. The tools to do it right will probably cost as much as someone
                  may charge to do it for You tho', so unless it's the experience You're in it for............................
                   
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                  • Rembrant

                    Rembrant Member

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                    Hi, this is an old thread but I see you have recent posts. I am in a similar situation only it isn't the return spring I am missing it is the pump drive spring. It goes on the other side of the diaphragm. Similar carburetor, a Holley 1920 but the not the same ID. Mines a 7583. I was wondering if you still had any 1920s laying around? I mainly need that spring but I would be willing to buy a whole rough one. I wouldn't mind also replacing the bowl cover on mine while I am at it. Someone figured if they just kept tightening the screws that pesky leak would go away. That's speculation but the the bowl cover is bowl shaped. I suspect it was caused by over tightening. I am just north of you in Vista. I just registered and have not found the PM button yet.
                    PS I am going out of town for 3 or 4 days so I won't reply until the weekend.
                     
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