In an internal combustion engine, valve covers, or rocker covers, are bolted over the rocker arm that opens and closes the valves. Internally, they consist of a baffle and a seal.
Valve covers are easy to over-tighten and, if you do so, you run the risk of warping or deforming them, which can cause leaks. Valve covers should be tightened to the torque, or twisting force, suggested by the manufacturer.
The recommended tightening torque for valve covers is in the region of 6 foot-pounds or 8 Newton meters (Nm) if you use a metric torque wrench. If you find that a valve cover leaks when tightened to this extent, you can tighten it slightly more.
Typically, valve covers are not under an immense amount of pressure and should not leak, provided the gaskets, or seals, are good and the valve cover is evenly tightened. You should coat the gaskets and the corresponding surfaces on the valve covers with sealer before tightening the valve covers.
