Abstract: A fuel calibration device is provided for replacing the original metering device associated with the carburetor and the fuel bowl of an internal combustion engine to enable the various fuel flows to be adjusted and calibrated. The metering systems of the device are accessible for interchanging them. A plurality of different metering systems are made available and changes are made by selection of the desired metering system. Provisions are made for changing idle jets, idle air, main system jets, main system air and main system emulsion tube.