Those Brazilian made engines are notorious for oil leaks. Power wash your engine and start with a new valve cover gasket. Fel-pro's are better thant he factory ones. When you remove your valve cover, clean the inside with oven cleaner. If your engine is full of sludge, start using a better oil in it!!! These engines cannot stand sludge build-up anywhere. Oil seals will leak if the oil pressure regulator becomes filled with sludge. Good luck!! You can get better power if you remove the stock plugs and install a set of Bosch Fusion or Platinum single points. Use Mobil One oil designed "for use in GM cars"
