1964-77 350cid 400cid 455cid Engine Valve Cover Grommet 1pc The cleaner valve breather slips into this grommet in the valve cover. The hole size is 1", not to be confused with the smaller grommet used on cars with NO valve cover breather. The small hole was only used on 1968 Olds engines. Dimensions: D shape hole in valve cover 1' round hole in grommet.