I never had to worry about this because even in my street days we raced every night so we kep our engine blowed out. Lol. But my uncle and old school mechanics kept n old 6.5 Oz coke bottles on their bench that they would fill with water and dump down the carb of a running engine before each tuneup. You wouldn’t believe the junk that cleaned out of those old lead loaded up engines. Carbon free in 30 seconds or less. Lol