A carburetor in 2023 (what you need to know)

A carburetor is the mechanical version of a fuel injector that is responsible for adjusting and mixing the air-to-fuel ratio in internal combustion engines.

While their use has declined since the introduction of electronic fuel injection systems, carburetors continue to hold a special place in the hearts of muscle car enthusiasts and owners of classic vehicles.

Therefore, in this article, we will go over what a carburetor is, how it works, the different types, how to clean them step by step, and more.

carburetor

What is a carburetor

A carburetor is the old mechanical version of fuel injectors.

The carburetor is in charge of adjusting and mixing the air-to-fuel ratio that is fed into an internal combustion engine’s combustion chamber. (1)

Carburetors were employed in the automotive industry for decades before the introduction of the electronic fuel injection system.

Nowadays, carburetors are almost exclusively found in smaller engines such as motorbikes, generators, and lawnmowers. However, they are still popular in muscle cars and other antiques since they are simple to work on, repair, and replace. They are also an icon for those types of cars.

How does a carburetor work

The carb is usually made up of the following components: a bowl for liquid fuel, a choke, a throttle, an idling jet, a main jet, a venturi-shaped air-flow restriction, and an accelerator pump.

Here’s how the following component works:

The basics (venturi effect)

A carburetor functions via an effect known as venturi.

The carburetor is connected to your engine’s intake and is located on top of the engine, beneath the air filter. As a result, when your piston performs its intake stroke, air flows through the carburetor.

The interior of the carb narrows towards the middle, where a fuel port is located, creating a venturi air-flow restriction. This restricting of the air results in low air pressure (venturi effect), which causes suction on the fuel port and hence draws fuel out of it in vapor form.

The venturi restriction forces fuel from the fuel port into the air stream at a rate proportional to the airflow, resulting in a practically constant fuel-air ratio.

The air and fuel vapors combine and are sent into the combustion chamber of your engine.

The bowl and jets

The fuel port we just went over is linked to what is known as the bowl. The bowl, as the name suggests, is a bowl filled with fuel.

It must be kept filled since otherwise your air-to-fuel ratio will be lost. This is why the float exists. As the fuel level drops, so does the float, allowing the bowl to be refilled through a fuel valve.

The float ensures the fuel level remains constant at all times.

The jets on the other hand sit inside the bowl, more precisely in the fuel. There are typically two jets, an idle jet, and a main jet. A jet is a small screw with a hole through it.

It is screwed into the port and the size of the hole determines the amount of fuel that goes through. Therefore, the hole size has a big impact on your air-to-fuel ratio.

The throttle valve and choke valve

The throttle and the choke inside your carburetor are both butterfly valves.

When starting a cold engine, the choke valve reduces air intake and permits a fuel-rich ratio to be provided to the cylinders. As the engine warms up, the choke is gradually opened either by hand or automatically by heat and engine-speed-responsive sensors.

The throttle valve control is usually linked directly to your gas pedal with a throttle cable. When you push on the gas pedal it pulls this cable opening the valve.

However, the throttle valve is always slightly open for idle, where the idling jet is utilized. When the valve is opened further the main jet comes into play.

There can also be an accelerator pump that injects fuel into the air when the throttle is suddenly and rapidly opened.

The Different carburetor types

The following list are the different types of carb configuration:

Typical Carburetors

  • SU Carburetor
  • Solex Carburetor
  • Zenith Carburetor
  • Carter Carburetor

The mixing process

  • Constant Choke Carburetor: Constant choke carburetors maintain constant air and fuel flow areas, with pressure variations or depression altering according to engine demand. Carburetors in this category include Solex and Zenith.
  • Constant Vacuum Carburetor: A constant vacuum carburetor, also known as variable choke carburetor, adjusts air and fuel flow areas based on engine demand, while maintaining constant vacuum. Carburetors in this category include S.U. and Carter.
  • Multi Venturi Carburetor: A multiple venturi system utilizes double or triple venturi, with the boost venturi concentrically within the main venturi. The discharge edge is at the throat of the main venturi, and only a fraction of the total air flows through it. The pressure at the boost venturi exit equals the pressure at the main venturi throat, and the fuel nozzle is situated at the throat of the boost venturi.

The number of barrels

  • Single 
  • Double 
  • Four-Barrel

Signs of a Failing carburetor (cleaning or adjusting)

The following list displays different symptoms that can mean your carburetor needs to be cleaned or adjusted.

  • Your engine won’t start
  • The fuel ratio is lean or rich 
  • Your engine’s performance decreased
  • Rough idling 
  • Your engine floods constantly

How to clean your carburetor step-by-step

Cleaning your carburetor is a very important maintenance work you need to perform.

As a good gauge and to be safe you should clean your carburetor every time you do an oil change. (about 3000 miles)

Cleaning your carburetor is a pretty easy job especially when you are used to doing it. Furthermore, it allows you to deepen your understanding of how they work.

To perform this job you will need to following things:

  • Safety: Nitrile Gloves & Safety glasses
  • Common hand tools: Screwdrivers & Ratchets or wrenches sets
  • Cleaning tools: Wire brushes, Circular wire brushes & metal wire
  • Unwanted fluids: Catch pan & Shop towels or rags
  • Cleaning products: Carb cleaner & Chemical dip

Cleaning a carburetor is not necessarily a dangerous job. However, wearing nitrile gloves and safety glasses is very important since carb cleaners and chemical dip products can be harmful to your skin and eyes.

Step 1: Remove the carburetor from the engine

The carburetor can be clean while still attached to your intake manifold however removing the carb completely takes 2 minutes and can make the job a lot easier. To remove the carburetor you will first need to remove the air filter.

Afterward, you can proceed to disconnect the carb and unbolt it from the intake manifold. Once the carb is removed it is advised to block the intake entry with a clean rag to avoid debris from falling in.

Step 2: Drain the carburetor

The carburetor bowl needs to be drained before you start. Therefore, you can either tip the carb upside down and let the fuel drain itself or you can remove the bowl right away and empty the fuel from there.

Step 3: Teardown the carburetor

Before proceeding to tearing down the carburetor it can be a good idea to do a quick cleaning of the outside of the carb. Once the outside is clean you can proceed to tearing it down one part at a time.

Every carb is different therefore there isn’t one fits all explanation and guide. However, you can find an organization method that works well for you to remember what goes where for the reassembling process.

Step 4: Start cleaning

Once you have all the parts laid out and organized you want to begin cleaning. You want to remove as much as you can before doing the chemical dip.

Removing the majority of the build-up will allow the chemical product to thoroughly clean every part of the carb. You can use the wire brushes to do so.

Step 5: chemical dip

After you’ve eliminated the majority of the gunk, you may begin lowering each part in the chemical fluid. Use a container big enough so that each part can be fully submerged.

The amount of time the part should soak in the product varies depending on the product brand. However, a reasonable range is between 15 and 30 minutes. To speed up the process you can dip more than one part at a time.

Step 6: Last cleaning & inspection

Now that your parts have soaked in the chemical dip it is a good idea to do a last inspection and cleaning. You will want to clean any gunk that may be remaining with the carb cleaner and your wire brushes.

At this stage, you should also look at the jets and the small port in the carburetor making sure they are clean and open. You can clean a clogged port using a thin metal wire and some carburetor cleaner.

Step 7: Reassemble and reinstall

Once everything is all clean you can follow the organization plan you made earlier to reassemble the carb and install it back on your car.

Different carburetor tuning adjustment

Adjusting the carburetor is a relatively simple job that can be done with a basic set of hand tools and a little bit of technical knowledge. There are many different adjustments possible on a carburetor.

Here is the common tuning adjustment for carburetors:

  • Choke Adjustment: Adjust how your choke valve is open when your engine is cold.
  • Idle Mixture Screw Adjustment: An air-fuel mixture screw on the carburetor controls how much air mixes with the fuel.
  • Idle Screw Adjustment: This will adjust how fast your car will idle. It is preferable to go according to your engine specifications.
  • Idle & Main Jet: These are your fuel jets. Usually changing them is unnecessary but it is still possible.

Are carburetors still worth it

Sadly enough the real answer on paper in terms of performance is no. Fuel injectors are a lot more performant, delivering better power, fuel economy, and lower emissions which is a standard for today’s cars.

Additionally, they can be precisely tuned with a computer in countless different ways to achieve a perfect solution.

However, in terms of “smiles per gallon”, for someone who enjoys working on their car, or for anyone owning an old classic they are absolutely worth it.

Carburetors will always be a loved icon in the muscle car world and if putting one on your big V8 project car makes you happy, go for it!

Conclusion

In conclusion, carburetors are mechanical fuel injectors that adjust and mix air-to-fuel ratios in internal combustion engines.

They were popular in the automotive industry before electronic fuel injection systems, but are now mainly found in smaller engines like motorbikes, generators, and lawnmowers.

Carburetors are iconic in muscle cars and antiques car worlds. They are also very simple to maintain, fix, and replace. They work by the venturi effect, using a bowl for liquid fuel, choke and throttle valves, idling and main jets, and a venturi-shaped air-flow restriction.

Despite the carb nostalgia, fuel injectors offer superior fuel efficiency, performance, and emissions control. For those who enjoy working on cars or classic vehicles, carburetors still hold value and provide a unique experience.