I had the same problem with my 57 235. I didn't have the block cleaned and I think the oil passage around the center passenger side head bolt was crudded up. Still don't know for sure. I had and extra head bolt and ground a groove through the threads of it and installed it in that hole. Fired it up and had oil to the rockers. I have also read about installing an unmatched head/ block combo & having to use a special head bolt to get oil to the rockers. Can't remember where I read it. Worked for me. I got about 5000 miles on it with no problems. I'll see if I can find the article with the answers. I have an 848 head on the 57 engine. Don't know the year of the head.
