- 1). Attach the vacuum gauge to the open vacuum port on your vehicle's intake manifold.
- 2). Review your carburetor or vehicle manual to determine how to reset the idle mixture screws. This is commonly done by turning the screw(s), found on the side(s) of the metering block(s), clockwise until they lightly bottom out, and then backing them out 1 to 2 turns, to establish a baseline for the tuning process.
- 3). Start the engine and turn each screw in 1/2-turn increments. Do not fully adjust one screw at a time, as the screws need to be tuned in unison to ensure the vacuum reading is correct.
- 4). Monitor the vacuum gauge as you continue to make 1/2-turn adjustments to each screw. When the vacuum pressure ceases to increase, despite another 1/2 turn, you've reached optimal vacuum pressure within the intake manifold. Sync the other screws by ensuring they have received the exact same number of turns -- syncing the vacuum pressure level.