Just inherited a 1969 Porsche 912 from my father. I have a general understanding of fuel injection from my days drag racing my nitrous assisted ’86 300ZX but I have no clue how a carburated car works and online articles are beyond me. Need the 5yo explanation because right now, it’s basically dark magic.
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The piston moves which draws air through the air filter and into a tube with a narrow portion in the middle. Then the Venturi Effect takes over, when air passes through a narrow opening it moves faster and reduces in pressure. There’s an opening in the tube where the narrow portion is and as the air flows into the narrow portion of the tube the pressure lowers and it pulls in fuel from a reservoir. The air and fuel mix and flow into the intake manifold then the combustion chamber where it’s ignited by a spark plug.
There’s a valve on top of the Venturi tube that can prevent the air from flowing in, that’s called a choke. When the car is cold it needs more fuel to ignite so the choke closes. There’s another valve at the bottom of the tube that allows more air to flow in, that’s called the throttle. Once the engine is warm allowing more air in pulls in more fuel and the process speeds up so the engine goes faster.
The bowl of the carburetor is the reservoir, it always has fuel on hand. That works like a toilet tank. There’s a float inside the reservoir, when the reservoir has fuel the float closes a valve and it stops more fuel from flowing in. As the fuel is used up the float falls and that opens a valve allowing more fuel to flow in.
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