Since it is a distal rocker arm that isnt oiling,I would first remove the side cover and visually inspect (including removing for cleaning, then replace) the oil hard line for kinks and restriction first.

Then, If you are very careful to not mix up the rocker arms/pushrods on disassembly, and do not tamper with the adjustment or cinch nuts, you might be able to get by without a valve adjustment and completely disassemble the two sides of the rocker shaft for inspection and cleaning.

Last edited by sstock; 03/16/2019 3:01 PM.
1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration