A; Drill a pilot hole then follow with a ¼” NPT tap into the valve cover exiting the right rear of the valve cover pointed towards the windscreen washer container. Use a ¼” pipe nipple (grind off the excess that protrudes into the interior of the engine so there is no chance of fouling the valve springs). The ¼” inside diameter is much too large for proper ventilation.
It must be reduced to 5/64”. I found it easiest to use my torch and solder several washers of descending size on the end of the pipe nipple, ending up soldering the pipe shut. Then drill that 5/64” hole through the solder in the middle of the smallest washer
Use a ¼” pipe nipple, it needs not be barbed – it’s a 95¢ hardware store item. That’s ¼” inside and ½” outside. It’s a taper fit into the valve cover so it’s tightened VERY snugly. But, again, grind off the excess that protrudes into the inside of the VC so it has NO chance of fouling the rocker assembly.
Hope this helps.
John Twist
SAFETY FAST!