ok,so some of u might understand now that the valve cover is not electrically continuous to the block (btw,i didnt say for all engines,im just talking about this one for now).

also some of you might understand now,that not all things are grounded just to complete a circuit & to make something work,there are lots of things involved in any electrical installation that need to be grounded/bonded/shielded/whatever in order to prevent undesirable side effects,there are lots of things that u could disconnect certain parts of the installation & everything would still work....but for how long? & how well would it work...how safe would it be?........