The lash vs. temperature change is a fight between the lifter and pushrod growth versus the upper block + head + valve growth. The pushrod being made of steel with the its higher thermal expansion coefficient, and being so long relative to the cast iron upper block, head and steel valve, means that pushrod side's growth is greater than the cast iron upper block, head and valve, and closes the lash with heat. So you gotta set it looser cold
Put some aluminum in the head and/or upper block and it expands so much faster than steel that upper block, head and valve growth dominates and opens the lash with heat. So you gotta set it tighter cold.
