How can I get my dog to slow down when eating?

We resued a pit bull about a month and a half ago. Every time we feed him he eats so fast he doesnt even chew. He just swallows his kibble whole. We think it may have somthing to do with him not being fed every day at his last home. We've tried just giving him small amounts through out the day and telling him "eat slow" and he gets it for about a minute and then starts eating really fast again. Any suggestions?