Carburetors
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Carburetors - Install, Repair, Rebuild and more!
The carburetor is a classic gas and air mixing chamber of an engine. The mechanics here at Big 3 Performance are the experts and the best for repair, installation, rebuilding and more in Green Bay, the fox valley and all of Wisconsin for your engine's carburetor. We will do our professional work on single barrel, 2 barrel and 4 barrel (4 BBL) carburetors. Our personal experience and expertise in the rebuilding and maintenance of these engines for our own vehicles, which are winning racing vehicles and street legal ones, too, is our assurance that we have the knowledge to offer you and give you the best service around. Big 3 Performance for your carburetor, to get you the best performance from your engine!
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If you have read the page entitled How Car Engines Work, you know that the idea behind an engine is to burn gasoline to create pressure, and then to turn the pressure into motion. A remarkably tiny amount of gasoline is needed during each combustion cycle. Something on the order of 10 milligrams of gasoline per combustion stroke is all it takes!
The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine "runs rich" and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The carb is in charge of getting the mixture just right. On new cars, fuel injection is becoming nearly universal because it provides better fuel efficiency and lower emissions. But nearly all older cars, and all small equipment like lawn mowers and chain saws, use carbs because they are simple and inexpensive. The carburetor on a chain saw is a good example because it is so straightforward. The carb on a chain saw is simpler than most carbs because it really has only three situations that it has to cover:
This short video of the carburetor (5.1 MB) takes you on a quick tour of the carb. Chainsaw carburetor Here are the parts of a carb:
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The carb is operating "normally" at full throttle. In this case the throttle plate is parallel to the length of the tube, allowing maximum air to flow through the carb. The air flow creates a nice vacuum in the venturi and this vacuum draws in a metered amount of fuel through the jet. You can see a pair of screws on the right top of the carb in photo 1. One of these screws (labeled "Hi" on the case of the chain saw) controls how much fuel flows into the venturi at full throttle.
When the engine is idling, the throttle plate is nearly closed (the position of the throttle plate in the photos is the idle position). There is not really enough air flowing through the venturi to create a vacuum. However, on the back side of the throttle plate there is a lot of vacuum (because the throttle plate is restricting the airflow). If a tiny hole is drilled into the side of the carb's tube just behind the throttle plate, fuel can be drawn into the tube by the throttle vacuum. This tiny hole is called the idle jet. The other screw of the pair seen in photo 1 is labeled "Lo" and it controls the amount of fuel that flows through the idle jet.
Both the Hi and Lo screws are simply needle valves. By turning them you allow more or less fuel to flow past the needle. When you adjust them you are directly controlling how much fuel flows through the idle jet and the main jet.
When the engine is cold and you try to start it with the pull cord, the engine is running at an extremely low RPM. It is also cold, so it needs a very rich mixture to start. This is where the choke plate comes in. When activated, the choke plate completely covers the venturi see this video of the choke plate to see it in action). If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet (since the end of the carb's tube is completely covered, all of the engine's vacuum goes into pulling fuel through the jets). Usually this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If you then open the choke plate the engine will start running normally.
This information is from the website www.auto.howstuffworks.com
When the engine is idling, the throttle plate is nearly closed (the position of the throttle plate in the photos is the idle position). There is not really enough air flowing through the venturi to create a vacuum. However, on the back side of the throttle plate there is a lot of vacuum (because the throttle plate is restricting the airflow). If a tiny hole is drilled into the side of the carb's tube just behind the throttle plate, fuel can be drawn into the tube by the throttle vacuum. This tiny hole is called the idle jet. The other screw of the pair seen in photo 1 is labeled "Lo" and it controls the amount of fuel that flows through the idle jet.
Both the Hi and Lo screws are simply needle valves. By turning them you allow more or less fuel to flow past the needle. When you adjust them you are directly controlling how much fuel flows through the idle jet and the main jet.
When the engine is cold and you try to start it with the pull cord, the engine is running at an extremely low RPM. It is also cold, so it needs a very rich mixture to start. This is where the choke plate comes in. When activated, the choke plate completely covers the venturi see this video of the choke plate to see it in action). If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet (since the end of the carb's tube is completely covered, all of the engine's vacuum goes into pulling fuel through the jets). Usually this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If you then open the choke plate the engine will start running normally.
This information is from the website www.auto.howstuffworks.com
A list of the many carburetors that we service at Big 3 Performance
Autolite
Bendix Carter Demon Carburetors |
Edelbrock
Holley Lectron Fuel Systems Motec Engineering |
Motorcraft
Pierburg Rochescter Products Division UCAL Fuel Systems |
Many more domestic
and imported carburetor manufacturers |
Dyno Tune Your Carburetor fed Muscle car, Sports car or Race car with
Big 3 Performance
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