Originally Posted by Dr. Isotope

The port on the valve cover that connects to the intake piping via a short hose is for crankcase ventilation, which vents fumes from the VC back into the intake tract, while maintaining pressure under the VC. It's necessary to the proper function of the motor. You know those little filters folks stick on the back of the VCs? Very, very bad.

So if your intake pipe doesn't have the port, make one.