846 inch diameter Venturi of the Model A carburetor. It still applies today as a great starting point. Go back to the adjusting screw on the carburetor throttle arm and adjust it to a low RPM, just faster than where engine tends to stall. Carburetors - Tillotson and Carter Tillotson Carb Repair. 00 Tillotson HR and HL Carburetor Diaphragm Rebuild Kit, Double Pumper.
