1989 Dodge Caravan New knocking

Hi there. I just bought a 89 Dodge Caravan and drove it home from Jersey to Ohio with no problem. Today, I took it to clean it out and check everything to the best of my knowledge, and all seemed fine. Got in and started down the road and suddenly have this random knock from the top of the engine. It now fails to run smoothly and it sounds like something is knocking from under the valve cover. I suspect a rod has broke or a spring, but am not sure. Your help would be amazing. Thank you.