auto diagnostic Once you have done this

How you can Improve a Holley Carburetor 1Turn your car´s engine off, lift the hood and locate your carburetor. Locate the carburetor´s two idle screws -- these are found on each side of the carburetor´s metering block Professional diagnositic tools, which is located between the body of the carburetor and the float chamber (depending on the model of Holley, there might also be an idle screw underneath the choke mechanism).

2Use a screwdriver to tighten the idle screws until you feel a slight resistance. Once you feel this, stop tightening the screws and start your car or truck -- let it run for five minutes.3Locate the carburetor´s vacuum port -- this is located on the underside of the main body. With the engine still running, remove the hose and then attach the vacuum gauge to the nipple from which you previously removed the hose.4Loosen the idle mixture screws and keep an eye on the vacuum gauge -- the screws should be loosened to where the vacuum gauge meter reads 600 rpm.

Once you have done this, stop loosening the screws and remove the vacuum gauge automotive diagnostic tool. Reattach the hose to the vacuum port and leave the engine running.5Locate the air/fuel ratio screw -- this will be located on the front of the carburetor, towards the bottom of the main body. With the engine still running, tighten the air/fuel ratio screw until you hear the engine sputtering. Stop when you hear this and then loosen the screw just past the point where the engine stops sputtering.