Need some help on pulley sizing

Not to argue with anyone but at one point I had a 64/65 street hemi crank pulley like 4.75 inches in diameter and ultimately when I swapped to a later equal size 5 and change water pump pulley sized one my car has stayed at 180 ever since. It was never hot but now it's super consistently at the same temp. As always the same disclaimer...."Yoir results may vary"