should I do this with the motor running or off
Engine running. By 58, they had eliminated the oil line under the pushrod cover and replaced it with internal passageways. They get clogged up pretty often. A quick fix that works sometimes is to remove the center head bolt in line with the pipe plug on the outside of the head, and insert a hardwood dowel rod that's a snug fit in the hole above the threads after filling the hole with oil. Smack the top of the dowel HARD with a BFH, and the hydraulic pressure will clear the passageways of accumulated sludge. If the oil flow is there, but very slow, the same process works with the engine running- - - -just let the hole fill with oil from the pump, and them hit the dowel several times. It won't hurt to run the engine for a while with one head bolt removed.
It's also possible to run an external oil line from the oil pressure port on the driver's side, around the back of the head and tap into the passageway that's plugged at the center of the head. A piece of 3/16" steel brake line works very well for the bypass.
Jerry
