ProPokerTools simulator says that if we give him a range of ONLY sets, all two pair, and straights (even all NS connectors/one-gappers), then we still have 41.2% equity. If we add in all the hands that might have an 8, like K8, T8, 98, etc, our equity goes to 52%.
If we include the times someone does this with hands like AT, JT, etc, it seems like it's a good spot to raise with the intent of GII as we definitley want to see two more cards. Although, I can get on board with just calling since if we miss the turn, we really only lost $40 more, but it would still feel crappy to have to fold to a turn bet.
BTW - In general, check raising only $40 more in this spot and this much money already in the pot certainly doesn't feel like a bet to try to protect a strong hand against a draw. It feels more like a top pair with a draw kind of hand trying to get you to fold two random overs, but sometimes people bet weird amounts on really wet boards, so i suppose anything is possible.