The ornamental design for a valvecover with breathertube, as shown and described.
FIG. 1 is a front left perspective view of a valve cover showing our new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof; and,
FIG. 6 is a top plan view thereof, the bottom view not being visible during ordinary use is not depicted.
The bottom view of the valve cover forms no part of the claimed design. The broken lines shown in the drawings illustrate portions of the valve cover that form no part of the claimed design.