take the side cover off, (big cover on side of block behind the dist.)look all the way to the rear you may see a small copper tube, it comes from the rear cam bearing and feeds the rocker arm shaft through a passage where the bolt you are refering to is. Take the copper pipe off and blow it out with compressed air, probably plugged up. I know some of the later engines don't have this as the passage was changed, but my 59 261 is not supposed to have it and did and it was plugged up, I cleaned it and it worked, I removed it and capped the passage at bothe ends and it worked even better. The moral of the story, you don't know what was done by who over the years so take time to check it all for possibilities. Also look in a shop manual, it will have a schematic of the oil passages.
