There is brass plug, on the front side of the head, near the deck, where the head and block bolts together, this was part of drilling to intersect two drill holes in the cylinder head to get oil from the block to the rocker pedestal to oil the rocker arms, then at the factory they plugged the drill hole with a brass plug. There is no quick fix for this, if the brass plug is completey missing, you will have to address this and more than likely pull the cylinder head off to do this, you need to tap for 1/16" npt plug, or set screw, or replace the plug which is not readily availalbe from vendors, but one could make one from brass round stock. This is under pressure, so it will not get better until addressed. By the way I could not see your pictures, but just fiquired out from rebuilding many of these heads over the years.