Adjusting an Edelbrock 1406 carburetor is a relatively simple engine maintenance task. Known for its simplicity, durability and performance, the Edelbrock 1406 requires no electronic equipment and no understanding of vacuum lines. In other words, adjusting an Edelbrock 1406 carburetor requires no prior knowledge of carburetors. An Edelbrock 1406 carburetor can be adjusted to prevent it from running too rich (i.e. too much fuel compared to air) or running with a mixture that is too lean on fuel.
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Start the engine and give it time to warm up to idle temperature. Locate the choke (located at the top of the carburetor) and make sure it’s fully open. It needs to be fully open so you can adjust the mixture screws.
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Adjust the air screw between the two mixture screws to an idle speed between 700 rpm and 900 rpm, depending on your engine, with the flathead screwdriver. Clockwise turns increase the rpm, while counterclockwise turns reduce the speed.
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Seat the flathead screwdriver into the correct mix screw. Turn the mixture screw clockwise while counting each full turn until the mixture screw stops are up against the carburetor body. Record the number of complete turns. Readjust the air screw until the engine idle speed is again between 700 and 900 rpm.
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Seat the flathead screwdriver on the left mixture screw. Turn the mixture screw clockwise while counting each full turn until the mixture screw stops are up against the carburetor body. Record the number of complete turns. Readjust the air screw until the engine idle speed is again between 700 and 900 rpm.
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Take the average between the full turns of the two mixture screws. For example, if the right mixture screw requires three full turns and the left requires four, the average is 3 1/2.
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Remove both mixture screws out of the carburetor body — by turning them counterclockwise with the flathead screwdriver (the average of the two original values). Readjust the air screw for idle, again between 700 and 900 rpm.