Feedback Carbs & Oxygen Sensors
The 5200 series carbs are "non feedback" while the 6200's are "feedback"
Feedback carbs have an electric solenoid that controls the amount of fuel delivered to the engine. This solenoid mounts on top of the carb, and extends through the fuel bowl into a cavity on the bottom which connects to the main jet passage. The solenoid has two fuel "inlet" holes on it's side, and one "outlet" on the bottom, it uses an o-ring to seal and keep fuel from flowing around it and going un-metered into the jet passage.
It is a "duty cycle" solenoid that replaces the power valve and simply turns on and off at different durations to meter fuel, much like a fuel injector.
The solenoid is "normally open" which means that if voltage is not supplied to it fuel will still flow through.
At the bottom of the solenoid is a threaded jet.The solenoid will have to be carefully held in a vice in order to remove this jet. When removed, a spring, seat and shaft will fall out. The spring keeps the seat off of the hole in the bottom of the jet, and allows fuel to flow through.When the solenoid is energized the shaft is pushed down, compressing the spring and pushing the seat ontop of the jet so fuel cannot flow through.
The computer controls the amount of time per second that the solenoid is energized, basing it's decisions on the oxygen sensor input.
The oxygen sensor is located in the exhaust manifold where it puts out 0-1VDC signal, where 0 volts means the engine is fully lean and 1 volt means it's fully rich. Around .5 volts is considered optimal for emissions purposes.
The sensor works because of the difference in oxygen content in the exhaust stream and outside of it. This difference causes an electrolytic reaction inside the sensor which causes it to put out voltage. The exhaust system must also be up to temperature before the sensor will work. Some vehicles have sensors that are heated through 12VDC
Note: If the sensor gets dirty, from carbon build-up due to the engine running too rich, it will malfunction and put out lower voltage then it should or no voltage at all. This makes the computer think the motor's running fully lean so it will put in more fuel which will just clog up the sensor some more. So make sure you're sensor is working with an air-fuel ratio gauge or check your spark plugs once in a while.
I recommend Bosch oxygen sensors. They warm up faster then the Farm & Fleet ones and cost about the same.
Carbon fouled sensors can usually be cleaned with a propane torch if you are careful.

Idle mixture adjustments
Most Mopar versions of these carbs have an adjustable idle mixture via an allen head screw at the base of the carb. This adjustment requires a 3/32" allen head wrench or a "flex shaft" tool available at many auto parts stores. Webers and older Holley's use a standard flat blade style screw.
Some carbs will have either a plastic or metal cap which would have to be removed to adjust the idle mixture.
Idle mixture should be adjusted with a vacuum gauge hooked up. Adjust the idle mixture screw to the position where you get the highest manifold vacuum reading and smoothest idle.
Auto trans cars like to have the trans in gear when setting the idle mixture (be sure to set the parking brake and chock the wheels first)

Electric Choke Operation & Adjustments
All Chrysler 1.7, 1.6 & 2.2 engines have electrically heated chokes. These have a heating element inside them that is warmed by electricity when the car is running. The choke only gets power when the engine has positive oil pressure (via the oil pressure switch). As the electricity heats the element up, it causes the choke to slowly open. The chokes on most models have a "vacuum kicker" that helps control the choke through engine vacuum. This allows the choke to open up a certain amount when the accelerator is pressed but the choke heating element hasn't warmed up yet.
The choke is connected to a fast-idle (cold idle) cam which increases engine idle when the choke is closed. As the choke opens, this cam rotates to different "steps" which result in lowering the idle speed down to normal (warm idle) when the choke is fully open. Fast idle is adjusted via a small screw attached to the fast idle cam which is almost impossible to see.

If the choke doesn't open up all the way by the time the car is warmed up, air-flow through the carb will be reduced and the engine will also run rich, thus losing power, fuel economy and producing more emissions. It can also keep the engine idling on the fast idle cam which can really be a pain.
Chrysler says their electric chokes are non-adjustable. However, early carbs & re-manufactured ones have "adjustable" chokes held together with screws.
To adjust these you simply run the engine until it's warmed up and the choke has opened to it's maximum position. If it isn't completely open, loosen the screws and rotate the choke housing until it's completely open. You should only be able to rotate it a little bit either way.
On cars with the non-adjustable kind you would have to drill out the rivets holding the choke together and carefully replace them with screws or replace the entire mechanism.

The Chevy & Ford versions of this carb usually use a water heated choke, which can usually be replaced with an electric one from a Chrysler or "newer" Chevy.

Jets
To replace jets you simply take off the top of the carb and they're right at the bottom of the float bowl. They use different jets then the standard Holleys so their regular jet kit won't work. A few jets can still be purchased from Holley individually if you want to pay $3 to $6 each; (holley p/n: 124-101 thru 124-589). Mopar Performance used to sell a kit (P4286777) with jets ranging from #159 to 455 but it's been discontinued.

Note: Some Weber & Solex carbs use the same jets as the Holley 5200s.

Early Holley and Weber/Solex jets are marked for orifice size in millimeters, while newer Holley jets are marked for flow rate in cm³/minute at 50bar. You can't always tell the difference between the old & new ones.
The chart below shows the relationship between jet size and flow rate. i.e: a new Holley jet marked 250 would flow approximately the same as an old one marked 135
This chart came from an old Holley 5200 tuning manual and has been 'projected' out to show conversions for the smaller size jets.

It is possible to tap out the threads on the bottom of the float bowl and use "normal" Holley jets. Standard jets have a ¼"x32 thread pattern. I have never done this myself but have talked to people that have..

Holley used to sell an electronic "dial a jet" package that would plug into a feedback carb, bypassing the oxygen sensor, and letting you control the amount of fuel through a dial on the dashboard. I would like to get hold of one of these control modules.
They even had a couple versions of "dial-a-jet" for the 4160 4bbls that used the same metering solenoids as the 2bbls.

Secondary Opening Rate
To change the secondary bore opening rate on a vacuum secondary carb, you have to open up the vacuum solenoid and change the spring inside. Use Holley's spring kit (p/n: 20-13), or Mopar Performance's (P4349320)
A lighter spring will make it open quicker, a heavier one will delay the opening. The springs are the same as standard Holley 4 barrel (41x0) springs and are color coded as follows:

Color	Load
White	Lightest (fastest)
Yellow (short)	Lighter
Yellow	Light
Purple	Med. Light
Plain (stock)	Medium
Brown	Med. Heavy
Black	Heavy (slowest)

There's only four screws on top to remove, be careful not to damage the diaphragm inside while removing the screws. I recommend brushing a "high-tack" gasket sealant on the surface where the diaphragm gasket touches the body.  This keeps it in place and prevents the tuner from accidentally kinking the gasket while putting the top back in place.
Holley doesn't recommend taking the spring out completely because without it the throttle plate might not completely close.

The black spring really delays the secondary opening a noticeable amount.
The difference with the lighter springs is harder to notice because there's a plate & torsion spring on the opposite end of the shaft (behind the throttle linkage) that's designed to keep the secondary from opening completely until the primary is fully open.
With the plate & spring removed the white & yellow springs bog a little and the white one doesn't always close back up when back off on the throttle.
Therefore I recommend removing only the torsion spring & leaving the return plate installed.

Holley has a "quick change" kit that lets you swap springs by only removing two screws (p/n: 20-59). It's designed for 4 bbl carbs but should work on our 2bbls just fine.

I have never noticed a performance increase from swapping vacuum secondary springs. The only reason I replace them on my cars is because the Chrysler feedback carbs have a vacuum secondary cover with vacuum fitting on it which connects to a solenoid which bleeds air out of the secondary diaphragm to keep the secondary barrel from opening when the engine is cold. I replace this cover with one from a "regular" 4bbl carb and use a light spring.

Accelerator Pump Modifications

You can increase (or decrease) accelerator pump capacity by moving the pump cam pivot pin up or down
putting the pin in hole one decreases pump capacity, putting it in hole three increases it.
Hole one will give better fuel economy, hole three gives better derivability.
Hole two is a compromise. Some carbs only have 2 holes.
All of my carbs were already set at hole 3 when I got them.

The accelerator pump system shoots fuel into the throttle bores when the throttle is first moved from the idle position.
The pump is designed to shoot fuel only into the primary bore, but can be modified to put fuel into both bores.
Note: putting fuel in the secondary bore is only good if the secondary throttle plate is open (ie: a 1:1 pri:sec opening ratio). Most of these carbs are set so the secondary opens at around 2000RPM, and by then the accelerator pump has already done it's job. This procedure comes from an old Holley tuning manual:
The accelerator pump "shooter" is just a little nozzle that sprays fuel.  On most Chryslers, the "shooter" only has one nozzle.  On other cars (chevy vega, chevette, pontiac sunbird, astre, ford pinto, mustang II, capri, etc.) that use the same carb, the "shooter" has two nozzles, but only one is drilled out.
To do this mod you need to replace your "shooter" with an older one from a vega or pinto and drill the secondary side out
You'll probably also have to cut a notch into your carb to accommodate the extra nozzle. (or replace you carb with a non-feedback one)
The factory one nozzle Chrysler has a notch in the primary bore where the shooter's nozzle sticks through.  The secondary side doesn't have the notch, so you have to put one there to fit in the double nozzle shooter. Also notch the spot directly above on the air-horn/float assembly.
You then have to drill out the secondary nozzle on your dual nozzle shooter.  Use a small bit that's the exact same size as the hole on the primary side of the shooter. Drill in the directions of the arrows in the picture on the left.
You'll have to mark the bit ahead of time so you don't drill too far through the shooter. The two holes must meet exactly together in the bend at the bottom end of the nozzle.
I've never tried this myself and I can't say for sure if it'll make you go faster or not. I doubt it would do anything on a normal vehicle.

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