I have this hole in my engine and my friends dad said that it is where the valve plug goes. He told me they are made of rubber and used to keep dirt out of the engine. Well I am wanting to know where I could buy said plug if that's what it really is. He is older and has had a lot of car/truck/mechanical experience so I trust he knows exactly what he is talking about. I will continue to look locally for this valve plug but I though I might as well try here as well.