I am not a mechanic. Learning as I go. I bought a 2002 Pontiac Grand Prix 3800 from a family member. The car has been sitting for about a year. He thought it was a blown head gasket. I changed the intake plenum valve gasket,valve cover gaskets,and the radiater. The sludge in valve covers were bad but i seen wors. It blocked the holes good. Cleaned that up. Changed oil. Drove good for five days. I changed the Map sensor to get check engine light off,which it did. Then almost immediately I heard a ticking knock. Sounds like it is coming from valve cover. It does not stop. Goes faster with speed. What should I do?clean oil pan and pick up