Are you talking about the red permetex in the spray can? I have tried that, and it seems like after awhile you still have a leak. I think part of the problem is that the head and the valve cover are made out of two different materials and expand and contract at different rates, so ther is always movement around the gasket. One thing I forgot to mention is to make sure the gasket serfaces on the valvecover are flat. If the gasket has been tightened to tight it will bend the valve cover in the area where the screw seats. I have had to straighten many of the valve covers in this area.
Hope this helps.
Jim
