Carbon on valves

Old school treatment done back in the day,,Rev engine to about 3,000 rpm and slowly dump (small amount at a time) a full glass of water in the carb to break up the buildup.In the 60's we did it at the Dodge Dealership, it was common for the people that didn't drive much or far.Good practice ? I don't know but it was what they taught back then.
Yep, works like a charm. Just don't pour too much in at a time. I remember in the late eighties my buddy had a water injection system on his '71 Roadrunner 383.