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How important is the Svc Bulletin "1/4" hole" in 2-barrel (supercharged) 289 WW2 carb?

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  • Fuel System: How important is the Svc Bulletin "1/4" hole" in 2-barrel (supercharged) 289 WW2 carb?

    Hi, rebuilt my original carb (correct for '57 Golden Hawk 289 supercharged) two years ago. Still plugging away. Noticed in Svc Bulletin (looking for carb box vent-flap settings) that a 1/4" hole was "now drilled" (Jan 1957) in the butterfly valve (see photo) to prevent "over-rich" condition when engine is cold. No way to get the butterfly off, screws are peened on back even if air-horn weren't in the way. Don't dare drill it and even with paper towels stuff down inside the carb, getting any shrapnel falling in there. Is that hole very important when it will never be driven in winter? (or maybe MORE so?). Call me lazy (frustrated at EVERY piece of this car fighting me? :-) but HATE to pull it all apart to drill one little hole.
    My air-horn IS 1 1/4" to prevent "lean condition after starting", so THAT change was made (my car is an early '57, Oct 18th 1956, engine 6100867). But a bit early for that hole in the choke butterfly.....
    Thanks Click image for larger version

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  • #2
    Thank you! I missed that one; I have that exact problem. It will'load up' when cold. Hpoefully I can get the butterfly out. (Don't, I say don't try to do this with the carb on the car!!!)

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    • #3
      I think i would "Fiddle" with the choke thermostat a bit. that would do the same thing without a lot of fiddlefarting around! Luck Doofus

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      • #4
        Doofus, do you mean adjust it more 'lean' (opens sooner), vs drilling the hole?
        I figured after looking at I can disconnect just that manifold pipe, and remove the top half of the carb and drill the butterfly; not terrible. (just seems I put thing together once, then take apart twice; and have not yet STARTED the car which assuredly will reveal MORE things that were not 100% the first time around). But funny you should mention the thermostat, because that was my next question. I tried to set mine after rebuilding, per the Shop Manual. But that references a "boss", which my casting does not have (see photo). Correct carb for the Golden Hawk, just doesn't have (or so faint I can't see it) the little 'boss' mark the manual points out on the side. What is the rule of thumb to set this to? I realize the odds are good I'll have to take the Supercharger box off (what a pain! That elbow is WAY oversized, quite the job to force it into place!) and adjust it eventually. But, maybe a guy gets lucky :-) Also wonder if there is really much POINT in the factory setpoint, after all these years, that thermostat coil isn't going to have the same properties it did when new. Anyway, any tips on where it should start out at? Minnesota but likely not driving it (assuming I live long enough TO drive it :-) ) outside the non-snow months!
        Click image for larger version  Name:	Choke setting.jpg Views:	0 Size:	42.7 KB ID:	1859338

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        • #5
          I would just set it to reliably close when cold.

          EDIT: not extra
          Gary L.
          Wappinger, NY

          SDC member since 1968
          Studebaker enthusiast much longer

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          • #6
            I don't think you need to take the Carb apart to drill a hole, just remove the Carb, Drill it, and blow it out with compressed air and reinstall.
            StudeRich
            Second Generation Stude Driver,
            Proud '54 Starliner Owner

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            • #7
              Yep thats it! look at the thermostat body, the fin on top is your reference point. you want just enough spring tension to barely close butterfly. once engine starts vacuum piston pulls butterfly open partially but fast idle stays engaged till you get warmed up and Blip the throttle. or take the carb top off, back up the butterfly with a piece of wood and drill it! if nervous at this i have a carb with 1/4 in hole already drilled i will trade ya! keep up the great work! Luck Doofus

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              • #8
                To the original question: If the Studebaker engineers thought it was important enough to design a fix and write a service bulletin about it... then it is important.

                Studebaker engineers knew a h**l of a lot more about cars than most backyard mechanics.
                RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

                17A-S2 - 50 Commander convertible
                10G-C1 - 51 Champion starlight coupe
                10G-Q4 - 51 Champion business coupe
                4H-K5 - 53 Commander starliner hardtop
                5H-D5 - 54 Commander Conestoga wagon
                56B-D4 - 56 Commander station wagon
                60V-L6 - 60 Lark convertible

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                • #9
                  Just offering options. Luck Doofus

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                  • #10
                    Originally posted by RadioRoy View Post
                    To the original question: If the Studebaker engineers thought it was important enough to design a fix and write a service bulletin about it... then it is important.

                    Studebaker engineers knew a h**l of a lot more about cars than most backyard mechanics.
                    I agree 100% with Roy on this one. But what I can't understand is what is the difference between drilling a 1/4" hole or just adjusting the choke leaner?

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                    • #11
                      Because----if you adjust it rich 1/32" too far it loads up and stalls. If it is 1/32" too lean it stalls. Every time you tinker with it, you have to take off the pressure box so a guy could spend days trying to find that 'sweet spot' And Roy is right: if they took the time to write a bulletin, they had trouble with it and they had a fix. And, yeah, they knew a heck of a lot more than us poor mortals.

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                      • #12
                        Thanks all.
                        One comment on the "if it's in the Service Bulletin..." I agree they knew a heck of a lot more than me, BUT, just with the little perusing I've done on the carb and such, I've seen them walk-back changes (like adding the carb-cover vent hole on the top, removing it completely, then adding it back in but on the side in JUNE of '57.) This "1/4 hole in butterfly" was ONLY January '57. Thus reasonable to wonder if they realized later that OVER-DID it and sometime later they removed it again (or made it 1/8"; or 3/4"). :-) In June I just see now they added MORE tweaks for hard-starting when hot, drilling holes in the base of the carb....... I need to read ALL the '57 (and into '58 I suppose) Bulletins in my PDF files.

                        Yeah Dufus, I'm going to just remove the carb top and drill the hole in the butterfly. Going to skip the June'57 "extra holes IF hard starting". Then IF I have hard starting, just as much work to do it then as now, with all the doggone plumbing inside the 'box' on the supercharged version that needs removing to remove the BASE of the carb. Have to remove the TOP of carb now anyway, as I notice they added a baffle by the float valve too (makes sense; my Model-A Ford is a pain when you brake for similar reasons, never solved). Have to make something up to fit I guess, just a piece of brass shim stock should do, but easy to do both now.

                        So, with choke, per the photo below, my 'arrow' is best-guess where my screw-driver is pointing. It was mostly obliterated by someone with a punch? But seem it must be 'it'? This is as-shown WHEN THE CHOKE IS JUST CLOSED. Therefore, to set per the manual "on the boss", I'd need to rotate it just a 1/4" of a turn counter-clockwise, That little-bit is all it takes then, eh? (65F here in Minnesota today, so when WARM seems it would possibly barely be closed). Well, 11 years, and you guys are still putting up with me. Thanks! (seperate post but STARTER SPUN HER OVER for the first time today; has not turned except with a wrench in 11 years since pulling the engine! :-) Gratifying to see the fan spin! Can't wait to actually hear it RUN the first time. Soon I hope?
                        Click image for larger version  Name:	Choke setting with butterfuly just closing.jpg Views:	0 Size:	63.1 KB ID:	1859624
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                        Last edited by bsrosell; 10-03-2020, 05:50 PM.

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