Abstract: A valve cover assembly for an internal combustion engine has an integrally formed spark plug tube extending therethrough and into a cylinder head. The blind joint between the spark plug tube and the cylinder head surface against which it abuts is provided with a unique joint seal assembly wherein a flange surface generally parallel to the cylinder head surface is provided on the outer periphery of the tube and the tube is reversely tapered from the flange to the end thereof. An elastomeric sealing ring is mounted on and retained in place by the reverse taper below the flange and abuts against the cylinder head. The ring is thus retained on the tube during installation and removal of the valve cover from the cylinder head while growth of the ring due to the hot oil environment is accommodated by the radial extent of the flange surface.