Engine Carburetor Upgrade Series Model 650 CFM Mechanical Secondaries Type ProformPROFORMs new 100 percent Aluminum Street Series Upgrade Carburetor is hand assembled in the U. S. The PROFORM Street Upgrade Carb Includes: Based on the wildly successful Billet Aluminum Street Series carburetors these Upgrade Series street carburetors are constructed of lightweight aluminum including changeable idle air bleeds for easy non permanent calibration changes if needed. Keep your drills in your tool box; fine tuning is accomplished by