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Discussion Starter · #1 ·
I have a 4100 on my 64. I dont think the secondaries are opening. I have read about a mechanical secondary kit people have used to convert, but have had no luck finding one on internet. I even contacted a source that sold them (now they just install them on rebuilds).
Does anyone have any links on this kit?
 

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I don't have any links to a mechanical secondary but I wonder - what opens them up? Linkage over on the choke side?
 

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Pull the top cover off the carb.
Flip it over, and you'll see the tiny air tube that controls the vacuum secondaries.

Make sure that passage isn't plugged up.

If I remember correctly (been a while since i had mine open), you should be able to take a vacuum pump and apply suction to the air passage and watch them open (or not open).

If that test doesn't work, I'd suspect a torn diaphragm.
 

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I agree to get the vacuum secondaries working correctly. They run really well when working right, and it's usually easy to get and keep them right. Mechanical conversions rarely work well, and are a PITA to tune well. That's likely why they no longer sell them to the public. If you really want mechanical secondaries, buy a Holley 4010 or a Summit M08750MS - both good carbs, designed for mechanical, and very similar to the excellent 4100. Personally, I'd stick with the fixed 4100.

David
 

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I have a 4100 on my 64. I don't think the secondaries are opening. I have read about a mechanical secondary kit people have used to convert, but have had no luck finding one on internet. I even contacted a source that sold them (now they just install them on rebuilds). Does anyone have any links on this kit?
Hey Mr. R_M,
Don't know about YOUR Autolite 4100's Secondaries not opening, but it is the adjustment of the Secondaries that provides the Initial Idle.

The Secondary Throttle Plates Shaft Adjustment Screw is supposed to be turned 3/4 of a turn past where it touches the Secondary Throttle Plates Shaft Adjustment Lever.

That 3/4 turn is supposed to open the Secondary Throttle Plates Shafts a bit which is from where the Air and Fuel cometh to provide the idle.

The problem with THAT is: 3/4 of a turn may be too much or too little and may need further adjusting.

BUT the problem with THAT is: In order to do any adjusting of the Secondary Throttle Plates Shaft Adjusting Screw, one has to remove the Carburetor from the Manifold because the Secondary Throttle Plates Shaft Adjusting Screw is not accessible with the Carburetor bolted to the Intake Manifold.

SIMPLE SOLUTION: Take the Secondary Throttle Plates Shaft Adjusting Screw in the Base of the Carburetor out and install a Hex Head BOLT with the same thread in THAT threaded hole.

The Hex Head BOLT will extend down into a recess in the Intake Manifold and is easily accessible with a small Wrench.

Doing this, makes the Idle Adjustment supplied by the Secondary Throttle Plates Shaft adjustable with the Carburetor on the Intake Manifold and the Engine running!

Did this on the Autolite 4100 1.12 C4AF9510-DG on Ms. American and it works GREAT!

JC
 

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Does it make a difference which carb gasket I use between carb and spacer? I have the 4 hole kind now. Would the big hole one unblock some passages?http://www.autoguide.com/mobile
You should always check to make sure that the gasket matches the bottom of the carb- ie, not blocking any passageways. With that said, the tiny air passage that controls the secondaries sits right out in the open over the nozzles. The big-hole vs. 4-hole isn't going to make any difference.

I forgot to mention- to test the secondaries with a vacuum pump, you're going to need either:
1. three hands
2. a helper
3. a brick

if you have 3 hands, use the third one to hold the primaries open
if you have helper, have them hold the primaries open
if you have a brick, sit it on the accelerator
 

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Discussion Starter · #8 ·
I think it's working now. I have new issues also. After running for a bit and shut off, it doesn't want to start. I have to keep cranking for up to 30 sec. before it starts. And it's not a smooth start. The starter has to walk it into running until the the engine overtakes the starter.



Sent from AutoGuide.com Free App
 

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I'd say that sounds like heat boiling the fuel out of the carb...but this is March.

Next time it doesn't want to start right up, stop cranking it and pull the top off the carb again...see what the fuel level looks like.
 

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When you're cranking and cranking on it are you holding the pedal to the floor til it starts? If it's flooding itself they will usually start right up when you do it that way. Just don't hold it there after it starts. That is a good way to tell if it's flooded or not. Might after driving it lift the hood and listen to see if you hear the hissing of gas dripping in the carb. That's how if knew for sure what my issue was with mine. But i was in the desert and even here it does it in summer.
 

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Hey Mr. R_M,
Don't know about YOUR Autolite 4100's Secondaries not opening, but it is the adjustment of the Secondaries that provides the Initial Idle.

The Secondary Throttle Plates Shaft Adjustment Screw is supposed to be turned 3/4 of a turn past where it touches the Secondary Throttle Plates Shaft Adjustment Lever.

That 3/4 turn is supposed to open the Secondary Throttle Plates Shafts a bit which is from where the Air and Fuel cometh to provide the idle.

The problem with THAT is: 3/4 of a turn may be too much or too little and may need further adjusting.

BUT the problem with THAT is: In order to do any adjusting of the Secondary Throttle Plates Shaft Adjusting Screw, one has to remove the Carburetor from the Manifold because the Secondary Throttle Plates Shaft Adjusting Screw is not accessible with the Carburetor bolted to the Intake Manifold.

SIMPLE SOLUTION: Take the Secondary Throttle Plates Shaft Adjusting Screw in the Base of the Carburetor out and install a Hex Head BOLT with the same thread in THAT threaded hole.

The Hex Head BOLT will extend down into a recess in the Intake Manifold and is easily accessible with a small Wrench.

Doing this, makes the Idle Adjustment supplied by the Secondary Throttle Plates Shaft adjustable with the Carburetor on the Intake Manifold and the Engine running!

Did this on the Autolite 4100 1.12 C4AF9510-DG on Ms. American and it works GREAT!

JC
You haven't the faintest idea how a 4100 Autolite carb works! You have your facts all wrong!!!
R
 

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You haven't the faintest idea how a 4100 Autolite carb works! You have your facts all wrong!!! R
Hey Mr. C,
Very interesting. Would you care to elucidate?

JC
 

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Hey Mr. C,
Very interesting. Would you care to elucidate?

JC
I was wondering if this would come up-

As far as i know- everything pertaining to the idle circuit is on the front half of the carb. That's where the idle air screws are, and when you adjust the idle speed screw, you're tweaking the front butterflies, not the rear.

that's not to say there isn't some sort of base setting on the rear butterflies, but i don't think it pertains to the idle, because there's no way to meter the idle fuel back there.
 

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Just like a Holley, the rear throttle plates are set to a specific opening to 'bleed' the rear bowl (more explanation for this elsewhere). From that point, the idle is adjusted from the front curb idle screw for air, and idle needles for fuel. The rear plates (butterflies) must be set properly to also get proper function from the front adjustments within their narrow range. The transition hole in the primaries should just be covered by the primary butterflies at idle. Stock engines with stock carbs should use stock settings.

Here is where it gets weird - JC's method allows the primaries to be set at standard factory settings (centered in the adjustment range, while the transition holes are covered), and roughly set the initial idle via the rear butterflies. This ensures the primary adjustments will be in proper range, and provide proper transition fueling for crisp driveability. It's a "quick trick", but the secondary adjustment should actually end-up at the stock setting (on a stock engine) if everything else is as it should be. So, use care with this trick, and generally only on modified or non-stock applications that require non-stock settings. If the secondaries need more than 1/2 turn or so from stock, you have other issues to deal with.

Modified PCV systems are one reason for using this method. Another example of an exception to the factory secondary setting is with healthy camshafts requiring higher stable idle at lower vacuum levels, where the rear plates may be opened a bit further to bring the front plates and adjustments back into their proper range again. Other mods may also be required. We pulled 440 dyno HP out of a 351W many years ago with a stock 4100 and minor adjustments like this. One of the best driving carbs ever made.
:tup:
David
 

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The screw should be backed off 3/4 turn from the point on the lever where the secondary plates are stuck in their bores. That is enough to unstick them.

Never heard anything about keeping them open to idle the engine. IIRC, the engine vacuum will normally pull the plates shut. At speed, the secondary diaphram pulls them open.
 

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I was wondering if this would come up-
Hey Mr. C,
It apparently came up today. :) So if we're going to have this discussion, and avoid any ambiguities, we should agree to use the Shop Manual Terminology, if THAT'S alright with you and Mr. Comechero. OK?

As far as i know- everything pertaining to the idle circuit is on the front half of the carb.
"EVERYTHING"?

That's where the idle air screws are,
The 1964 Ford & Mercury Shop Manual calls these components "Idle Mixture Screws". What you are calling "idle air screws", I shall henceforth call "Idle Mixture Screws". OK?

The reason I question your term about "EVERYTHING pertaining to the Idle Circuit is on the front half of the carb" is because in Group 10, Part 10-4, Page 10-39, under the Sub-Head: IDLE FUEL SYSTEM, the Shop Manual says:

"The difference in pressure between the fuel bowls and the idle discharge ports forces fuel through the primary and secondary stage idle fuel systems."

and when you adjust the idle speed screw, you're tweaking the front butterflies, not the rear.
Alright.

The 1964 Ford & Mercury Shop Manual calls these components "Primary Throttle Plates" and "Secondary Throttle Plates". What you are calling "front butterflies" and "rear butterflies", I shall henceforth call "Primary Throttle Plates" and "Secondary Throttle Plates". OK?

At this point permit me to mention that in Group 10, Part 10-1, Page 10-6, under the Sub-Head: SECONDARY THROTTLE PLATE ADJUSTMENT - 4-BARREL CARBURETOR, the Shop Manual says:

" 1. Hold the secondary throttle plates closed.
2. turn the secondary throttle shaft lever adjusting screw out (counterclockwise) until the secondary throttle plates stick in the throttle bores.
3. Turn the screw in (clockwise) until the screw just contacts the secondary lever.
4. Finally, turn the screw 3/4 turn clockwise for the correct setting."

that's not to say there isn't some sort of base setting on the rear butterflies, but i don't think it pertains to the idle, because there's no way to meter the idle fuel back there.
The above quote out of the Shop Manual refers to the "base setting" of the Secondary Throttle Plates. And the opening of the Secondary Throttle Plates using the Secondary Throttle Plate Adjusting Screw, provides a small amount of air and fuel to go into the Intake Manifold.

It has been my personal experience to, after having replaced the Secondary Throttle Plated Adjusting Screw with a Hex Headed Bolt, to while the Engine is running, increase and decrease the Idle Speed of the Engine with the Hot Engine Idle Speed Screw completely off of its pad, which renders the Primary Throttle Plates COMPLETELY closed, and the Fast Idle Screw not in contact with the Cam in the Choke Mechanism, which also renders the Primary Throttle Plates COMPLETELY closed.

This is NOT theoretical. This is an ACTUAL fact. I have personally done it. The idle speed of an Engine with an Autolite 4100 C4AF-9510-DG Carburetor can be increased and decreased using the Secondary Throttle Plate Adjusting BOLT.

This is not to say that the Engine's idle speed cannot also be increased and decreased using not only the Idle Mixture Screws, the Hot Engine Idle Speed Adjusting Screw, AND the Fast Idle Screw, but if you think that the Secondary Throttle Plates cannot, by adjusting the Secondary Throttle Plate Adjusting Bolt acting against the Secondary Throttle Lever, increase and decrease the Engine's idle speed, you are mistaken.

And my ORIGINAL comment was about making the adjusting of the Secondary Throttle Plates a simple operation by installing a Hex Headed BOLT that could be accessed while the Carburetor was on the Intake Manifold AND the Engine running, rather than having to take the Carburetor off of the Intake Manifold to adjust the Secondary Throttle Plate Adjusting SCREW which CANNOT be done while the Carburetor is installed on the Intake Manifold.

Anyway, was kind of taken aback by the accusatory tone of Mr. Comechero's response to my post. Would like to ask you: Do you think I need a Defense Attorney? :)

Looking forward to YOUR response, and to Mr. Comechero's reaction.

Be well.

JC
 

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man, its a tough crowd today. :)

a couple of things i'd like to point out:
my tone wasn't accusatory.

i put the "as far as i know" part in my original post for a reason. i am in no way trying to sell myself as the end-all Autolite wizard. so when i said "As far as i know- everything pertaining to the idle circuit is on the front half of the carb." that's what i meant. Don't read too much between the lines.

Now- back to our conversation...

Sure, we can use the shop manual terminology.

I never said that the idle speed couldn't be changed by moving the "Secondary Throttle Plates". I would imagine that you could prop them open with a screwdriver and run it right up to redline.

I think maybe we're not asking the right question to get the answer that is in the shop manual.

To borrow from your post:

1. Hold the secondary throttle plates closed.
2. turn the secondary throttle shaft lever adjusting screw out (counterclockwise) until the secondary throttle plates stick in the throttle bores.
3. Turn the screw in (clockwise) until the screw just contacts the secondary lever.
4. Finally, turn the screw 3/4 turn clockwise for the correct setting.

Notice that nothing is said here about monitoring idle RPM while making this setting. Its just 3/4 turns clockwise after contacting the secondary lever.

So- is this setting attempting to reach a specified idle RPM, or is this just cracking the secondaries open a bit to get them out of the bores?
 

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man, its a tough crowd today. :)
Hey Mr. C,
When the going gets tough, the tough get going! :)

a couple of things i'd like to point out: my tone wasn't accusatory.
I know that. It wasn't YOU whose tone was accusatory, it was Mr. Comechero's.

What I said was: "Anyway, was kind of taken aback by the accusatory tone of Mr. Comechero's response to my post."

i put the "as far as i know" part in my original post for a reason. i am in no way trying to sell myself as the end-all Autolite wizard. so when i said "As far as i know- everything pertaining to the idle circuit is on the front half of the carb." that's what i meant. Don't read too much between the lines.
Wasn't reading between the lines of YOUR post. It was fine.

Now- back to our conversation...

Sure, we can use the shop manual terminology.

I never said that the idle speed couldn't be changed by moving the "Secondary Throttle Plates". I would imagine that you could prop them open with a screwdriver and run it right up to redline.

I think maybe we're not asking the right question to get the answer that is in the shop manual.

To borrow from your post:

1. Hold the secondary throttle plates closed.
2. turn the secondary throttle shaft lever adjusting screw out (counterclockwise) until the secondary throttle plates stick in the throttle bores.
3. Turn the screw in (clockwise) until the screw just contacts the secondary lever.
4. Finally, turn the screw 3/4 turn clockwise for the correct setting.

Notice that nothing is said here about monitoring idle RPM while making this setting. Its just 3/4 turns clockwise after contacting the secondary lever.
Actually, the Shop Manual says that the setting of the Secondary Throttle Plate Adjustment is done with the Carburetor on the bench.

My modification of putting a Hex Head BOLT in place of the Secondary Throttle Plate Adjusting SCREW was done so the Secondary Throttle Plate Adjustment could be done ON the Intake Manifold with the Engine running.

So- is this setting attempting to reach a specified idle RPM, or is this just cracking the secondaries open a bit to get them out of the bores?
It seemed to me that it was done to make the Engine run so that all the OTHER adjustments could be made.

That I have been experimenting with ALL the adjustable features was just for my own enjoyment and education.

As was mentioned previously, was a bit taken aback by Mr. Comechero's comment: "You haven't the faintest idea how a 4100 Autolite carb works! You have your facts all wrong!!!", and am wondering what it was that I wrote that elicited THAT kind of reaction?

Am still awaiting his elucidation. Hopefully all this hasn't put him off.

JC
 
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