How to Adjust Holley Carburetors

Carburetors are vital for the functioning of the engine. Holley carburetors are very popular because these do not cause much trouble, and are easy to maintain. Holley carburetors do not have many moving parts and thus, does not lead to much wear and tear. These carburetors can be tuned easily, and have easy availability of spare parts and upgrades. If your vehicle has a Holley carburetor, learn how to adjust a Holley carburetor, so that you can keep the carburetor clean and fine.

Equipments needed for this adjustment:

You need simple instruments like a wrench set, a screwdriver and a voltmeter to adjust the Holley carburetor. Except the voltmeter, you get other instruments with your vehicle usually. If you do not wish to buy a voltmeter, you can borrow it from some one.

Procedure to adjust a Holley carburetor:

  • Detach the car’s air cleaner. Opening throttle linkage by a slight turn will help you in choke adjustment, and then turn it back to the same position. The choke has to be completely closed. If the choke is not closed completely, using the screwdriver, loosen the screw in the black colored ‘choke-spring housing’, turn it in clockwise direction to close it completely, and then fit the screws tightly.
  • Switch on the engine of the vehicle. Choke plate of the engine gets heated after starting the vehicle for sometime. At 1500 RPM, the engine stands at fast idle and choke plate opens approximately after two minutes. When you snap the engine’s throttle linkage quickly, it will put the engine on slow idle.
  • Using the voltmeter, you can check the power in the coil spring to check the working of the choke. If the voltmeter indicates power in the coil spring, it means that the coil of the choke is bad, and needs to be replaced.
  • Shut down the engine of the vehicle. There are some sight plugs located towards the passenger side seat of the carburetor which you will have to unscrew
  • Let the engine be switched and keep adjusting the mixture continuously.
  • The 650 CFM’s have two screws under the engine’s carburettors, and the engine’s ‘large-board carburettors’ have four screws.
  • First start adjusting the screw by turning it to the side of the driver seat. Then start turning the screw towards the right, and keep turning it till the engine’s rpm drops.
  • Again stop and start turning the screw towards left, so that the engine’s rpm reaches to its highest point.
  • Again turn it by a quarter turn to its right.
  • Follow this with the other side of the screws as well. After having done with it, once on both the sides, repeat the procedure once again on both sides.
  • The next step is adjusting the actuating arm of engine’s accelerator pump. You can see a nut at the point where this pump comes in contact with the engine’s throttle linkage.
  • Using a wrench, start turning the nut. Turn it till the arm pump beneath the float bowl starts moving, and the engine’s throttle linkage moves by approximately a quarter inch.

The procedure requires time and is difficult to a certain extent. However, adjusting the Holley carburetors once or twice yourself will help you understand better.


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  3. How to Adjust Throttle Position Sensor
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  5. How to Adjust Bike Gears

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