The stock ductile iron rocker adjusters are either 3/8x24 threads or if they have been upgraded and blue printed they would be 7/16x20 so when you due the math on the thread sizes for 1 Inch it works out to be on the 3/8x24 one ful turn of the adjuster equal .0416666 , I round it up to .042 per thread. The 7/16x20 equals .050 per turn, correct so that means a 1/4 turn on the 3/8 equals right at .0105 per 1/4 thread and the 7/16 equals .0125 per 1/4 turn.
Keep in mind the adjuster is on the short side of the rocker arms so the adjustment is multiplied on the valve stem side by the ratio of the rocker arms
I would start with 1/2 to maybe one full turn cold and go from their based on the iron block with aluminum heads and aluminum rocker arm stands, look at the time slips for guidance