it does however move vertically when i rev the engine but returns to horizontal position at idle even when hot and with no tension on spring is this normal?????
Once the engine speed rises above idle, the exhaust volume and extra heat will make the bimetal spring lose more tension and the flap valve will go to the full-open position. If you're a brave soul, try propping the hood partway open and riding the fender to watch the valve while a friend takes a drive around the block!
LOL!
Jerry