What I mean is to take a piece of steel or aluminum or brass rod that is the same diameter as the oil hole in the head, that comes up through the rocker bolt hole, cut it off to about 3/4" long, then file a flat along the length of the rod, to allow oil to pass by. If there was no flat, the oil hole would be plugged. You don't have to have much of a flat, remember that a 0.070" diameter hole in a Holley jet makes a good restrictor.