Motorcraft 2100 Technical

Runs Bad Over 1/2 Throttle

The engine bangs out really bad as if it's not getting enough fuel. I don't know the history on this engine, it has been rebuilt, not sure if the cam in stock, it does have headers on it. Is it possible that I need even larger mains?

A new ignition control module fixed it!!

What Does The Float Spring Do?

I have a damper spring on my float pivot rod. Currently it is oriented with the short side under the float hinge and the long side against the back of the float bowl (behind the needle) ...in effect putting slight up pressure on the float. The spring is in its natural state, i.e. not wound around giving more tension. Is this correct?

The spring is used to keep the float from bouncing. A small amount of tension is desirable. If it is flopping around then wind it one turn. From what you describe you have it in the right position.

Where can I Get the Vent Tubes & How Do I Replace Them?

The tubes can be found here:

These tubes are pressed in. You should be able to move the tubes back and forth while pulling on them. You can also drill them out, just be careful not to drill too large. Install by tapping them in gently.

How Does the Choke System Work
Watch a video:

Power Valve Bad

My thoughts are they installed the power valve incorrectly. The newer power valves use a large gasket that fits into a grove a the edge of the power valve sealing surface. I hold the carburetor upright as I screw the power valve and gasket into the main body. This operation is complete when you see the gasket is securely seated into the grove on the lip of the power valve. If not seated correctly it will damage the gasket and the power valve will leak like it is ruptured!! The same thing will happen if they use the wrong gasket for the two different power valves with different sealing surfaces. The newer power valves use the perimeter thick gasket and the older ones use two different types. One gasket is thick and triangular on the inside ( probably the correct one for Ford 2100 &2150) and round on the outside. The other is thinner in thickness and diameter and has three or four tabs on the inside to keep centered on the power valve. (used more often on spark valve like the 1100 carb) You look at both older gaskets to see if they seal to the mating surface on the main body. Possibility that the venture cluster air bleeds are plugged. Remove the carb air horn then the cluster and blow out passages in main body and the cluster assembly, Don't forget to remove the pump discharge check ball and weight!! Maybe a bad power valve if installed correctly??

I had gotten a 4008 kit from you for my 2100 autolite 2bbl. I was wondering which hole the little red plug goes into in the acc pump location. Mine has a center hole and one right under it..i think it goes in center

The red silicone rubber (inlet check) goes in the center hole of the main body. The other hole is the inlet for fuel to refill the accelerator pump cavity. After the pump discharges thru the squirt nozzle the lip of the red silicone check lifts and fuel refills the pump cavity. Caution when installing the rubber check by lubricating the stem or it might break!! Thanks JIM L

PPower Valve Vent

Any gas coming out of this hole indicates a bad power valve, or the power valve gasket is damaged.

When I pour gas in the fuel bowl in order to test the pump, all the fuel leaks out the bottom. Is that supposed to happen??

Is the power valve installed. It resided on the bottom. If it is installed, then it might be leaking.

Ford/Motorcraft 2100 Carburetor FAQ

Q: What is the Ford/Motorcraft 2100 carburetor?
A: The 2100 is a two-barrel downdraft carburetor widely used by Ford and AMC on V8 engines from the late 1950s through the 1970s. Known for its simplicity, reliability, and ease of service, it remains a popular carburetor for classic car restorations.

Q: What is the best way to disassemble the 2100 carburetor?
A: Take plenty of photos during disassembly to aid in reassembly. Use a cookie sheet to keep parts from rolling away. Avoid removing the throttle shaft, throttle valves, or choke shaft unless absolutely necessary, as these are difficult to reassemble correctly.

Q: Are there any special tips for cleaning the 2100 carburetor?
A: Disassemble the carburetor fully (except for rubber and electrical parts), soak metal components in Simple Green for two hours, then rinse with hot water. Blow out all passages with compressed air, ensuring small holes are clear. Soda blasting can also help with stubborn deposits. If corrosion is severe, replacement may be necessary.

Q: Should I use sealant on the gaskets?
A: No, do NOT use any gasket sealant, as gasoline can break down the sealant and clog the carburetor’s small passages. Always install gaskets dry.

Q: How do I test the float for leaks?
A: For brass floats, immerse in hot water and watch for air bubbles (which indicate leaks). For plastic or nitrophyl floats, weigh them and compare the weight to the specification. Replace if out of spec.

Q: How do I handle multiple gaskets in a rebuild kit?
A: Kits may include extra gaskets for coverage across various models. Use the gasket that fits best for your carburetor, even if it needs trimming. Don’t worry if mounting gaskets have extra holes that don’t align with anything, as some are casting holes.

Q: What is the best way to clean idle mixture screws?
A: Use a soft wire wheel for cleaning. If you see scoring (from over-tightening), replace the screw.

Q: Can I use WD-40 as a lubricant on my carburetor?
A: No, avoid WD-40 as it can react with ethanol and cause gumming. Use silicone spray lubricant for gaskets if needed.

Q: Any advice for carburetors on engines that have sat for months?
A: If your engine has been sitting for six months or more, the fuel in the tank has likely gone bad. Clean the gas tank and fuel lines thoroughly—simply flushing with new gas is not enough.