Decarbonization flush

The buildup is on the neck of the valves preventing the
full retraction of the valve on each cycle, leaving a
slight slack at the top when the rocker arm is already
coming back down. tick-tick-tick-tick.

While I can picture what you’re describing, if that is indeed what is happening, why isn’t it quickly causing a burned valve?

Good question. As mildly as I drive this truck, ( 140k is LOW mileage for a 92 ) perhaps that is the reason for BOTH the carbon buildup ( only 1/2 mile to work ) and not damaging it worse.