Find another YFA with the same base that isn't worn.
You got a 2060 carb body casting number for Carb No 2 , with some kinda 644x throttle body casting number.
and 2138 carb body casting number for Carb No 3 , with some kinda 644x throttle body casting number.
A 7115S throttle body might work.
Find another 1-11/16 th throttle body YFA carb. They are all pretty much alike.
The stock 300 big six jet was 104-105-106 to 107 thou jet size. Which you can still get anywhere from Edlebrock.
Most most Metering rods (aka needles) were sized for an engine with bang on 114 net hp at the flywheel. Which is what a 170 hp Gross 300 was.
The 1987-1997 EFi made about 170 hp net due to the headers, ignition and intake improvements.
There are other smaller main jets in the 92 or 98 thou sizes for the small sixes. These were made to calibrate the carbs air fuel right down for engine ratings of 75 hp for the 170 cube Maverick (105 hp Gross) or 83 hp net 200 Falcon or Maverick sixes (115-120 hp Gross).
On LTD's or F100 with the 240 Bid Sixes or the Mustang 250 or Ranchero 250's, which were about 93-99 hp net , the factory 140 to 155 gross rating engines used another jet size and another thicker metering rod.
AMC Jeep 199's and 232's put out about 85 to 100 hp net, so any jet and metering rod combination for an AMC YFA will be rated about the same as a 240/250 or 300 metering rod and jet combination.
So you can lean or richen up the whole engine by estimating how much flywheel hp you'll make net. Each one of the three carbs is only looking for about 60 hp net of fuel, so if you can find thicker metering rods from the 170, 200 or 240 with some smaller 92 to 98 thou jets, that might get you into the right air fuel mix zone easier.
But you know, I'd say what you have right now will allow you to find a good metering rod profile.
If the cam is stock, then it'll not make anymore than 175 hp net at best when all three carbs are jetted bang on. So I'd say the ideal jet sizes are what serves the needs of each group of two cylinders.
The best carb is the a brace of three two step EECIV or MCU truck feedback carb's. The little 2.5 XJ Jeep or Ranger 2.0 or 2.3, or the so called troublesome 4.9 Big Six feedback carbs from 1981 to 1986.
They are able to use the MCS adjuster to sweep the air fuel ratio right into the sweet 12:1 for power and 16.1 for cruise value with any one of the stock metering rods and main jets. You adjust the air fuel ratio by duty cycle (read....pulse width). You run that by tuning the duty width off a MegaSquirt MS2E control box, that also allows you to use the stock TFI EFi igntion. There is a rich or lean Mixture Control Solenoid, one for the 2.0/2.3 Ranger or 2.5 Jeep, and another for the 4.9 Big Six.
Ford and AMC started ditching that technolgy in 1985, not because its sucked, but because the EPA had other better regulatory ideas that ment Carter carb production was unecconmic. Port EFi became the only game it town.
The YFA is the best carb ever made. You just have to find the right parts.
"Converting to a Carter YF and Throttle Cable" viewtopic.php?f=1&t=72607&p=562727#p562727
"Flat spot with Carter YFA" viewtopic.php?f=1&t=76774
"Surging with a Carter YFA? " viewtopic.php?f=1&t=76871&p=591996#p591996
"Need sizing for a carb for my 68 F100" viewtopic.php?t=77315
My standard offer is this:
Black Hawk Engineering do a reprofilr service for sub 94 thou jets
To Choose dimensions for a new metering rod.
The example here is for a 94 thou jet single YH Carter side draft, but all the YF's and YFA's share the same metering rod shank dimension capabilities
If you have measured air/fuel ratio numbers for cruise and power, you can then adjust the flow areas proportionately.
For example, if you have a power A/F ratio of 11 to 1 and you would like to have a ratio of 12 to 1, the ratio is 11 divided by 12 or .92. If your current power flow area is 300, multiply .92 times 300 equals 276. Look in the General tables for the jet size you are using and find the flow area closest to 276. Then read the corresponding metering rod diameter. Do the same type of calculations for the cruise step.
Our current manufacturing process is limited to diameters of .054 to .094".
If the metering rod you want falls outside of this range, you will have to choose another jet size to find a combination that works. The available jet sizes are .077, .080, .083, .086, .089, .092, .095, .098, .101, .104, .107, .110, .113, .116 and .119"
That then means tracking down a common junked Jeep 258, 2.5 liter I4, Ford 0HC 2.3, 170/200/250/240/300 jet. You'll get lucky enough from from this...I'll help out, its just math. You'll just have to warm up your car up for 10 minutes, and get C02 readings or air fuel readings.
Then you tell me what your metering rod codes are, and i'll tell you how to get the right Air fuel ratios from the existing needles.
Jetting is based on having a good ignition advance curve, and the right plug heat range. With a wide band and actual air fuel readings, you can dial in or out fuel just by swapping main jets and metering rods. There are hunders around, and the latest Edelbrock 1400 series carbs have the same min jets as the old YF, as well as simiar metering rod profiles. So you just look up the Carter YF jet tables, and find a leaner or richer Metering Rod and jet combination to suit. No different to tuning an AFB, or Rochester Quadrajet.