Carburetors Function and History

The history of classic car carburetors is a fascinating journey through the evolution of automotive technology. Carburetors were once an integral part of virtually every gasoline-powered vehicle, playing a crucial role in mixing air and fuel for combustion within the engine. We join up with carburetor expert Scott Bares of Classic Mechanics Garage in Appleton, Wisconsin, to help us gain a better understanding of the carburetor’s history and function.

Scott points out to fully understand carburetors you need to understand how they evolved in the classic car. He adds, here is a brief history of carburetors in classic cars:

Early Carburetors (Late 19th Century): The concept of carburetion dates back to the late 19th century when the first internal combustion engines were being developed. Early carburetors were often simple devices consisting of a chamber where fuel was mixed with air before being fed into the engine.

Updraft Carburetors (Early 20th Century): In the early 20th century, updraft carburetors became popular. These carburetors were mounted on top of the engine with the air intake below and the fuel mixture drawn upwards into the engine.

Side-draft Carburetors (Mid-20th Century): Side-draft carburetors, where the air intake and fuel mixture entered the engine from the side, gained popularity in the mid-20th century. They were more compact and allowed for better engine packaging.

Down-draft Carburetors (Mid to Late 20th Century): Down-draft carburetors, which became prevalent from the mid-20th century onwards, featured the air intake from the top and the fuel mixture drawn downwards into the engine. These carburetors were more efficient and offered better performance.

Decline in Carburetors (Late 20th Century): With the advent of electronic fuel injection systems in the late 20th century, carburetors began to decline in usage due to their limitations in fuel efficiency, emissions control, and performance.

Bares further explains, despite the changes in design over the years, the primary function of a carburetor is to mix air and fuel in the correct ratio for combustion within the engine cylinders has remained unchanged since its invention. Understanding each of the carburetor’s functional processes is key to understanding how they all work together, here’s a closer look at how it all works:

Air Intake: Air enters the carburetor through an air intake orifice, where it passes through a filter to remove any impurities.

Fuel Delivery: Fuel is delivered into the carburetor either by gravity feed or through a fuel pump. The fuel is stored in a reservoir (bowl) within the carburetor.

Mixing Chamber: Inside the carburetor, the air and fuel are mixed in the correct proportion based on the engine’s requirements. This mixture is then atomized to ensure proper combustion.

Venturi Effect: The carburetor utilizes the Venturi effect, where the airflow through a narrowed section of the carburetor creates a low-pressure zone, drawing fuel from the reservoir and mixing it with the incoming air.

Throttle Control: The amount of air entering the engine is controlled by the throttle valve, which opens and closes in response to driver input via the accelerator pedal. As the throttle valve opens wider, more air and fuel mixture are allowed into the engine, increasing power output.

Idle Circuit: The carburetor also has an idle circuit to supply a small amount of fuel and air mixture to keep the engine running when it’s not under load.

While modern cars have largely transitioned to electronic fuel injection systems due to their improved efficiency and emissions control, classic car enthusiasts often cherish the nostalgia and simplicity of carbureted engines, keeping the legacy of these mechanical marvels alive.