Sending you a PM. Don't want to .

 

Looking at my 1972 2100 Motorcraft carb, I had some observations.

I took another look at the emulsion tube cluster. Clean as a whistle, except the buildup on the emulsion tube holes.

It has a number stamped in it, JJ2 B3. Wonder what that means?
There are holes down both sides of the tube. Having cleaned them up with a hot solution of vinegar, I see there is a problem. Several of the holes have cracks between them. I could feel the cracks with a thumbnail before getting the light just right, and seeing them clearly. A hand lens is a good tool for this.

If it gets any worse, I may try silver-soldering the cracks. First, I would want to find out what the hole-size is exactly. I didn't have a drill-bit that size, and the torch-tip cleaners are not the right tool for the job.

Maybe condensation gets down in there, and freezes? I know for sure that this carb has never been handled roughly. Also, the inner tube inside the emulsion tube is off-center in both. One moreso than the other.

Using a new, Forney brand torch tip cleaner, I 'measured' the hole at the end of the inner tube, and it nicely matches a #12, or 65-67 'drill', as provided on the back of the cleaner-holder-tool chart. I did not change the size of the hole, nor those in the emulsion tube.

I did check if the emulsion tube would come out of its seat with gentle persuasion, and no... it stuck in there tightly. One is rotated differently than the other. To get it out, I think it would require heat on the aluminum part, and cooling the tube simultaneously with cool water. Not sure on the method, just passing on tips from other carburetors.

On a tangent, ...
Putting it back together again, I did wonder about the pin-weight on top of the check-ball. Kits come with two sizes of this, and I'm wondering if I noticed, and just stuck the larger and heavier one in. Does anyone know which one is correct? The second weight is about a forth of the mass.

 

pin gauges, sometimes call go/ no go guages are about the most accurate way to measure on the cheap.

 

In case some of you didn't see my other posts on this issue, I replaced my factory 55 jets with 59's and it completely cured the problem. The truck is now fun to drive. My theory is simply that the 10 % ethanol just doesn't have the same btu content as good old gasoline. I remember when I first tried 10 % ethanol in my weed eater, I had to crank out the main and idle mixture screws before it would even think about running. This should have been something that clued me in long before now. Remembering things like this is very helpful over the years and decades. I know racing engines running alcohol have to have huge fuel flows due to this same issue.

 

Idle circuit probably provides the same amount of fuel throughout the RPM or throttle range, but it's like a squirt gun compared to a firehose in terms of effect at those speeds. Each circuit should be looked as a standalone or distinct system, there is some interaction but they should be tuned independent of each other and not adjusted to compensate for a problem in another circuit.

 

Emulsion tubes are just pressed in. Most are not centered, that's just variation in design. Though not intentional, it does not affect the operation of the tubes. Regular solder will solve the crack issue. Cracks form because of a stress riser present in manufacturing. Heating and cooling cycles make them run. The gas does not get as hot as the motor, or at least shouldn't in a properly maintained system, so regular solder will not reflow. Later emulsion tubes actually were closed on the bottom. Emissions carbs are like this.
The carb is a designed system with specific choices as to the booster venturi assembly, spreader if present, bleed hole sizes and the body size. Different bodies of the same throttle bore size, say 1.14, will have different sizes and number of slots and holes which tune the idle circuit and its further contribution (as it does always contribute) throughout the position of the butterflies. I had considered making a flow bench to characterize various boosters and carbs years ago. This is really what you would need to properly characterize any change you wish to make. I have three 2100's that I milled the front mount deck off to make a tri-power setup. The center carb is a manual choke 1.23 truck carb (crossover passage at bottom of booster), and I have two sets of outboards: a 1.14 set and a 1.08 set, both identical carbs. I have played with 2100's for years, and the one thing I can tell you is when you start mixing and matching booster venturiis with different bodies you run into tunability issues. That's why I look for originals at car shows. The ones that have been rebuilt - even the ones rebuilt by Holley - have mixed and matched parts and while they 'work' they never tune up as well as an all original. The two things that are easy to swap on the 2100's are jets and power valve. There are also a number of positions in the various linkage connections and you can set the fuel height in the bowl. Bob Mannel's Small Block Ford book is an excellent resource on the various carb settings for the carbs used in Ford's car lines. You can read between the lines in that data to come up with interesting settings for your own application. For instance, early 289 4V's had the 1.12 4100, and not the 1.08 4100 that came later. So for all the people that say a 1.12 is too much for a small block, apparently Ford didn't think so. But bolt a T-bird 4100 on your 289 without adjusting something (like jets) and it will run like crap. Just another example of how lore creeps into existence.
Link to book:
MUSTANG AND FORD SMALL BLOCK V8 BOOK 1962-1969 VOLUMES 1 AND 2