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View Full Version : What is the purpose of the magnet on the choke plate?


Yadkin
09-29-2012, 04:58 PM
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.

KULTULZ
09-29-2012, 06:25 PM
:confused: Magnet?

simplyconnected
09-29-2012, 07:05 PM
Yeah Gary, I've never heard of one an any carburetor.

KULTULZ
09-30-2012, 04:43 AM
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.

Yadkin
09-30-2012, 11:35 PM
You guy's haven't seen the magnet? :confused:

http://i514.photobucket.com/albums/t345/Southernmanpics/TBird/magnet.jpg

Part #77

KULTULZ
10-01-2012, 02:43 AM
I haven't. :confused:

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

KULTULZ
10-01-2012, 03:51 AM
:o

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.

Yadkin
10-01-2012, 10:03 AM
I haven't. :confused:

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.

Yadkin
10-01-2012, 10:22 AM
:o

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.

KULTULZ
10-01-2012, 10:43 AM
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.

:rolleyes:



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.?

KULTULZ
10-01-2012, 10:44 AM
Oh...BTW...

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

Yadkin
10-01-2012, 11:42 AM
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?

KULTULZ
10-01-2012, 02:14 PM
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/1958/Service/index.html

jopizz
10-01-2012, 04:18 PM
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

Yadkin
10-01-2012, 05:09 PM
.

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/1958/Service/index.html

I have the '64 shop manual (an original) and it says nothing about starting procedure.

KULTULZ
10-01-2012, 07:03 PM
I have the '64 shop manual (an original) and it says nothing about starting procedure.

Starting procedure will be described in the Owners Manual.

I was just conveying why the setting is called for.

Yadkin
04-03-2013, 11:58 AM
OK I think I have a clue about this magnet. Or more mystery about my carburetor, I'm not sure which one. :o

According to the GP Sorenson instruction sheet for the 4100 F4, there are three different automatic chokes, '61 and earlier, '62-4, and '64 and later. None of the diagrams show the magnet.

For the '64, Sorensen says the choke pull-down is adjusted by a nylon not attached to the lever on the choke shaft, essentially changing the length of a control rod. My rod is a fixed length, just like the earlier chokes. But I don't have the adjusting screws shown on the '62-3; mine has to be adjusted per the '61.

Sorensen has instructions to adjust the magnet just as John has described, and that diagram shows the non-adjustable rod.

My carb #C4SF B "matches" what was installed in 1964, and my tag matches the stamped number on the base plate of the main body.

KULTULZ
04-03-2013, 01:22 PM
Your carburetor is correct-

C4SF-B
C4SZ 9510-A
MPC 9510 Parts List 17Q
Magnet- Choke Plate C2SZ 9E585-A

There were several different choke designs as well as carb asm deviations. This is why it is so important to have that ASM. I.D. NO.

Yadkin
04-03-2013, 06:01 PM
What is "asm"?

KULTULZ
04-03-2013, 07:23 PM
ASSEMBLY

As In Assembly I.D. No.

davidmij
05-29-2013, 12:18 AM
WOW! No wonder I had such a hard time getting my carb set up and running half decent. I changed the top plate from my existing 67 LTD 390 and put it on a 1969 Mustang carb that I used because the secondary vacuum pickup tube had broken on the old one. I bought the second carb for $40 for parts. The one has the plastic adjustable choke lever, the other doesn't. Amazing how many little changes they made year to year.

Yadkin
05-29-2013, 02:47 PM
Not only year to year but possibly mid-year and rebuild kits sometimes have parts that have to be substituted in order to make other parts work.

For instance on my 64 Bird 390 the vacuum secondary diaphragm is "male", and the steel lever that acts on it is "female". Even the kit instructions don't know which one I'm supposed to have; you have to remove the cover to see. Many parts manufacturers only make the "female" diaphragm and supply a "male" nylon lever to replace the OEM steel "female" lever.

A replacement male diaphragm is much more expensive, if you can find one. I have discovered a way to convert a replacement female diaphragm to a male, by using a short #6 machine screw and threading it into the hole. That way I can use the OEM lever and the carb looks original on the outside.

Here's a picture of it showing the outside of the diaphragm and the OEM lever. I powder coated the steel parts to mimic cadmium plating.

davidmij
05-30-2013, 11:03 AM
I ran into that too Steve. I think it was my original carb on my 352 in my 59 T-bird. I modified it with a screw as well. Mikes carburetors has all the right parts and kits. They seem to be a little more expensive with a standard rebuild kit, but they can get you ALL the correct parts. See their rebuild video in the technical resource section.

Dave J

Yadkin
05-31-2013, 12:18 AM
Yeah I've bought one from Mikes before. I think it was $30, while a female was ten. Six months later, a different car, different carb and I ordered from a cheaper site and ended up with a female part. Stuck a screw in and lucked out.