Uni-Sync Is A Precision Instrument That Provides A Visual Method Of Balancing The Performance Of Each Carburetor In Multiple Carb Set-Ups With A High Degree Of SKU. 4025 ; Details. Edelbrock UNI-SYN "A" Carburetor Balancing instrument ; Documents & Installation Notes · PDF-Installation Instructions ; UPC, 00085347040254. The easy solution is simply to open each idle screw 1/2 turn before you lock the throttle shafts together. However, the tool is relatively inexpensive (if you With the UNI-SYN Adjusting Screw (A) approximately 1/2 open, place the instrument over the throat of No. 1 carburetor and hang the Sight Tube (C) on a Very well made tool. Key is to 'breifly' hold it over the throat of the carb. Once the ball is centered (ish), move to the next carb and Edelbrock 4025 Uni-Syn Carburetor Synchronizing Tool · Designed to work on small, one barrel and two barrel carbs (downdraft or side-draft) · Fits carb necks from