Your opponent made a Bluff-call on the flop just to bluff you on a turn. You should encourage him to do so and bet 33% of the pot so he can re-raise quickly you and then say all in and sit back in your chair. If he thinks about calling, just say to him that he propably has you beat but you had to try That should make his decision making even harder if the 8 helped him (maybe he was in with 78s).