The heads you all are thinking of are 54 and newer. A 51, 235 is just like a 216. It oils through a removable tube that runs through the pushrod compartment, up through a hole in the head and attaches to the oiler on the center of the rocker shaft. It does not oil through a center head bolt. Without removing the crank and the cam I see no way of clearing the internal oil passages. Air didn't work. What is surprising to me is that the lifters seem to be pumping up. But, they are probably getting oil from the front oil passages.I'd put a quart of tranny fluid in the oil but then the lifters will collapse.
Glenn,
