Here are some pictures on how to modify your Power Valve Channel Restriction (PVCR) circuit on your Holley carb. It is not very difficult and can make an incredible difference on how your car drives. To tune this circuit you will need a wide band O2 sensor.
Step #1: Drilling out your PVCR
Step #2: tap out the PVCR, We like to use 6-32, some prefer 8-32.
Step #3: I like to use a cordless drill to hold the set screw while I drill out the center.
Step #4: Here you can see the jet we are about to install into the PVCR
Step #5: The completed PVCR mod
