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What is the purpose of the magnet on the choke plate?

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  • What is the purpose of the magnet on the choke plate?

    It seems to me that it shuts the plate completely and makes it harder for the choke spring to pull it off. When I set the choke on mine I keep the plate slightly open when cold. I'm concerned otherwise that the engine wouldn't start.

  • #2
    Magnet?

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    • #3
      Yeah Gary, I've never heard of one an any carburetor.
      My latest project:
      CLICK HERE to see my custom hydraulic roller 390 FE build.

      "We've got to pause and ask ourselves: How much clean air do we need?"
      --Lee Iacocca

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      • #4
        Originally posted by Yadkin View Post

        It seems to me that it shuts the plate completely and makes it harder for the choke spring to pull it off. When I set the choke on mine I keep the plate slightly open when cold. I'm concerned otherwise that the engine wouldn't start.
        There is no magnet, other than the magnet offered years ago to supposedly increase fuel mileage and lessen occurrences of vapor lock...

        The choke cap spring is the only method by which the choke plate closes. The introduction of heated air (choke stove hot air in this instance) expands and lessens the tension of the spring gradually opening the choke plate.

        There is an adjustment to be made (manual choke pull-off) when the carb is cold that will either increase/decrease this tension. When the choke is set, the choke closes completely and this is when that adjustment is necessary.

        The Shop Manual has a very good description of the theory.

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        • #5
          You guy's haven't seen the magnet?



          Part #77

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          • #6
            I haven't.

            What series 4100 do you have (year-model)?

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            • #7


              OK...

              While living with old age insomnia and this subject absolutely driving me up a wall, I think I have found the answer.

              On the instruction sheet you showed, it appears as the original instruction sheet included in the FORD kit. Look @ PG 03 and you will see in one box- CHOKE MAGNET & BRACKET ADJ.

              I believe this to be an early method of ensuring the choke plate staying (allowing for pull-off adj) closed while cranking on early models. I found an application on a 58 MERC 1.06. It does not show on the 58 MERC 1.19

              It must have been used on a very few early 4100 models. Later design used linkage adj. to hold the choke plate closed.

              The kit (AUTOLITE/MOTORCRAFT C2SZ 9A586-D) was designed finally to include most all service parts for most all models/variations over the production years.

              I am pretty sure that is what this feature is (was) designed for. And I don't ever remember coming across this or I just didn't realize what I was looking at.

              Now maybe I can fall asleep...

              Is Yadkin your name or home in NC? I used to live in EDEN/STONEVILLE.

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              • #8
                Originally posted by KULTULZ View Post
                I haven't.

                What series 4100 do you have (year-model)?
                Mine is a late 1964 for a base 390. This kit sold at Mike's Carburetor Parts is #438 for various engines (from a 289 to a 428!) between 1958-1969.

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                • #9
                  Originally posted by KULTULZ View Post


                  OK...

                  While living with old age insomnia and this subject absolutely driving me up a wall, I think I have found the answer.

                  On the instruction sheet you showed, it appears as the original instruction sheet included in the FORD kit. Look @ PG 03 and you will see in one box- CHOKE MAGNET & BRACKET ADJ.

                  I believe this to be an early method of ensuring the choke plate staying (allowing for pull-off adj) closed while cranking on early models. I found an application on a 58 MERC 1.06. It does not show on the 58 MERC 1.19

                  It must have been used on a very few early 4100 models. Later design used linkage adj. to hold the choke plate closed.

                  The kit (AUTOLITE/MOTORCRAFT C2SZ 9A586-D) was designed finally to include most all service parts for most all models/variations over the production years.

                  I am pretty sure that is what this feature is (was) designed for. And I don't ever remember coming across this or I just didn't realize what I was looking at.

                  Now maybe I can fall asleep...

                  Is Yadkin your name or home in NC? I used to live in EDEN/STONEVILLE.
                  That's a plausible explanation. With my old-age eyesight I did not see the adjustment instructions for that (figure 12). Mine closes tight, and it needs to be set at 0.010". Apparently this gives a super-rich shot of fuel if you cold crank before opening the throttle to achieve the 1/16" opening from the choke unloader (figure 15).

                  Yadkin is the name of a river that I live near. I'm located about an hour west of Eden.

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                  • #10
                    Originally posted by Yadkin View Post

                    That's a plausible explanation. With my old-age eyesight I did not see the adjustment instructions for that (figure 12). Mine closes tight, and it needs to be set at 0.010". Apparently this gives a super-rich shot of fuel if you cold crank before opening the throttle to achieve the 1/16" opening from the choke unloader (figure 15).
                    That design must have been some stop-gap measure on some applications. Is this feature on your 4100 and what was the original application?

                    Simply put, when the automatic choke is set (depress accelerator pedal fully once) and the choke plate closes, it cannot close fully or the engine will starve for air @ start-up. That measured (spec) gap has to be in the choke plate to air-horn for proper start-up.

                    If the engine refuses to start on initial firing, one depresses the accelerator fully and holds to engage the manual choke pull-off feature (also an adjustment). This will allow enough air to start if the engine has not flooded.



                    Originally posted by Yadkin View Post

                    Mine is a late 1964 for a base 390. This kit sold at Mike's Carburetor Parts is #438 for various engines (from a 289 to a 428!) between 1958-1969.
                    I missed your post. Do you think the carb was original equipment on the 64 or was it from another application?

                    Did it have an Assembly Tag I.D. No.?
                    Last edited by KULTULZ; October 1st, 2012, 08:49 AM. Reason: SHORT EYEBALLS

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                    • #11
                      Oh...BTW...

                      THANX for calling me on this as it is my newly learned factoid of the day. I had no idea...

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                      • #12
                        Yes, the carb is the original. I've owned the car since 1987, and I'm fairly certain that no one had even tinkered with the carb before I got it. It has the assembly tag but the car's at the shop now.

                        Yeah you're right the choke pull-off occurs when you fully depress the throttle. Maybe the magnet engages with a partial depression? I'm more of a "visual" type and will have to have the carb in my hand and play with it a bit to figure out what the purpose is. But 0.010" doesn't allow much air in at all.

                        Perhaps I should read an owners manual for a clue. Is there a pdf version available somewhere?

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                        • #13
                          Originally posted by Yadkin View Post

                          Perhaps I should read an owners manual for a clue
                          .

                          You need the correct year Shop Manual.

                          Is there a pdf version available somewhere?
                          This is a 58 but will give you some info for yours-

                          http://www.tocmp.com/manuals/Ford/19...ice/index.html

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                          • #14
                            According to the instructions I have the 0.010 measurement and the magnet need to be adjusted with the choke thermostat temporarily turned to 90 degrees closed as far as the mark goes.

                            John
                            John Pizzi - Squarebirds Administrator

                            Thunderbird Registry #36223
                            jopizz@verizon.net 856-779-9695

                            http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

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                            • #15
                              Originally posted by KULTULZ View Post
                              .

                              You need the correct year Shop Manual.

                              This is a 58 but will give you some info for yours-

                              http://www.tocmp.com/manuals/Ford/19...ice/index.html
                              I have the '64 shop manual (an original) and it says nothing about starting procedure.

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