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  #1  
Old 03-19-2013, 10:33 AM
Yadkin Yadkin is offline
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Default Autolite 4100 binding

I'm rebuilding the carburetor and having a problem with the secondary throttle shaft binding. This has been a problem for a while and since it had been rebuilt in the past I figured I or someone else had screwed up somewhere. Since the shaft binds the vacuum secondary barrels does not work and I basically have a 2bbl carb.

The entire unit was gummed up terribly so I dismantled it completely including the throttle plates and gave everything thing a good soak. After degreasing I dipped all the steel parts in muriatic so all the rust is off. Brass got treated with muriatic to clean off any loose iron rust or aluminum deposits. I soaked the aluminum in dilute boiling vinegar. I then rinsed everything for a long while in hot water, dried, then fine wire brushed polished and cleaned everything.

For those who may be unaware, muriatic will dissolve aluminum in an exothermic reaction, so don't treat aluminum that way. There is a product called Acid Magic that is muriatic acid stabilized in some way so it releases far less noxious gas when treating rusted steel.

I cleaned the shaft bores with a fine wire gun-barrel brush and the shafts with 600 grit sandpaper. A light coat of WD-40 and they turn nicely with no excessive clearance or binding. That is, until I install the plates on the secondary shaft.

Throttle plates are oval, not round, since they seal a round hole at a slight angle. The plate edges are machined at that same angle. Put them in upside-down and they will bind as the sharp corner contacts the soft aluminum barrel; right-side-up and they seal perfectly without binding.

The primary plates have a bevel at the upper surface facing the front of the carb to reduce the plate thickness slightly. This allows more precise interaction with tiny sensing holes in the side of the barrel; three lined up vertically. One of the plates has a tiny factory indent at the front edge that lines up with at least one of the holes and I'm not sure why. Is there a right and left plate? The sensing holes in the right and left barrels appear to be identical. I installed the screws, tightened them down and the shaft turns without binding.

The secondary plates have no thickness bevel but because of the edge bevel they only go in one way. When I put them in and install the screws the shaft turns freely and the plates seal perfectly. However when I tighten the screws the shaft binds. The plates do not appear to be perfectly flat, so when tightened against the weak brass shaft it apparently bends it and hence the binding. I switched the plates right to left and no difference.

What am I doing wrong?
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  #2  
Old 03-20-2013, 09:25 AM
KULTULZ
 
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I am E-MAILING Ray a few pages out of the SHOP MANUAL concerning dis-assembly/assembly.

Read the pages carefully. There are considerations to be taken during dis-assembly/reassembly.
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  #3  
Old 03-20-2013, 09:43 AM
Yadkin Yadkin is offline
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I tested the secondary diaphragm with a vacuum pump and discovered it was clogged up. The vertical hole cleaned up nicely by turning a 1/8" drill bit by hand. When I went to clean out the horizontal shaft I discovered what appeared to be copper wire jammed in there. Apparently a previous rebuilder wasn't so careful. So I started exploring with a tiny bit on a dremel and the tip broke off.

One thing led to another and now I have several broken tips in there, and no way to get them out. The only way I can fix it is to rig up a tube from the sensor port and thread a fitting on to the diaphragm chamber.

But this together with the shaft issue tells me that this main body is done. I need a new main body or a new carb altogether.
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  #4  
Old 03-20-2013, 10:23 AM
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Default Autolite 4100 binding

Here are the pages that Gary sent me. I hope that they help.

http://www.squarebirds.org/picture_g...CarbRefurb.htm
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http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm
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  #5  
Old 03-20-2013, 10:31 AM
KULTULZ
 
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Quote:
Originally Posted by Yadkin View Post

But this together with the shaft issue tells me that this main body is done. I need a new main body or a new carb altogether.
Is the carb correct for the engine (stampings on LF mounting foot correct to CARB I.D.)?
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  #6  
Old 03-28-2013, 01:33 AM
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Quote:
Originally Posted by KULTULZ View Post
Is the carb correct for the engine (stampings on LF mounting foot correct to CARB I.D.)?
Yes it is a C4SF B. I was lucky to find the same number on ebay; it came today and is in great shape. I was careful to number the throttle plates before disassembly, I'm sure that they were never removed before because of the way the screws came out, and I'm happy to say that I got it right with my old carb.
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Old 03-28-2013, 01:35 AM
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Quote:
Originally Posted by YellowRose View Post
Here are the pages that Gary sent me. I hope that they help.

http://www.squarebirds.org/picture_g...CarbRefurb.htm
Thanks. I've got the original factory repair manual for the car and it details the carb assembly very nicely.
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  #8  
Old 03-28-2013, 02:08 AM
KULTULZ
 
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Quote:
Originally Posted by Yadkin View Post

Yes it is a C4SF B. I was lucky to find the same number on ebay; it came today and is in great shape. I was careful to number the throttle plates before disassembly, I'm sure that they were never removed before because of the way the screws came out, and I'm happy to say that I got it right with my old carb.
TALK ABOUT LUCK...
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Old 03-29-2013, 05:24 PM
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Originally Posted by KULTULZ View Post
TALK ABOUT LUCK...
I must be livin' right.

A saw a picture of a 4100 from pony carbs and the steel hardware was all plated cadmium yellow. Is that correct for my 64 Bird? If so I may powder coat the stuff that color.
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  #10  
Old 03-30-2013, 01:48 AM
KULTULZ
 
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Check out these plating products-

http://www.eastwood.com/underhood-en...il-paints.html
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