This handy 1/8" NPT female bulkhead adapter is popular for installing in valve covers when trying to measure engine vacuum.
Simply drill a hole and fasten our 9832-02-2 adapter to the inside of valve cover providing a leak-free O-ring seal. 
Valve cover must have flat surfaces on both the inside and outside where being installed.
 
             
             
                     
                     
                 
                 
                 
                