I have been TRYING to create HUGE grain.... I wish I had your secret.
Here's something to think about. What you are seeing as grain on paper isn't really grain. Grains are black spots on negative. So on paper, they appear white. If you are seeing BLACK spots on paper, that is a space between grains on negative.
As such, light and white area on print, thus dark and dense area on film, tends to exhibit more of this kind of thing. Layers of grain stacked up on film emulsions letting very little light through in fewer spots. So these area are less dense (on paper) and appear more grainy.
A lot of this is normal but it's hard to say without seeing what you are talking about.