I have a 2007 1.8 engine. Two cylinders had 30 psi compression, so I removed the head and found badly burned exhaust valves. There is a screen in the block. When I was cleaning the head bolt holes with a shop vac the screen came out. One end is open and the other end is closed. My question is which direction is it installed? What is it's purpose? Which hole does it go in? Thanks for your help.