EarlyHemi rocker arm shafts do not receive a continuous oil supply and they do not receive massive amounts of oil unlike many other v-8 engines. The oil that is supplied by an oem pump in good working order is adequate for all but the most severe applications.
The camshaft directs oil to the rockers through the 2nd and 4th bearing journals; the 2nd journal feeds the driver side at the 2nd rocker arm stand and the 4th journal feeds the passenger side shaft through the 4th stand.
The holes in the journals are approximately 0.156″ dia.
The passenger side is fed at TDC and the driver side is fed at 255 crank degrees.
Additional oil supply can be provided by enlarging the holes in the journals to approximately 0.185″ but should not be larger. Recall that the oil drain back holes through the head are limited in size and excess oil can cause leaks at the corners of the valve covers. Additionally, excess oil on the top end will be a reduction in oil available to the crank bearings and lifter galley.
If the oil supply to the top end seems inadequate then you should first check to insure that the holes in the block, between the cam and the deck, are clear as well as the holes through the heads and that there is no restriction at the head gasket.
A common restriction is sludge build-up in the rocker arm stand, however, the most common restriction is in the shaft itself. If the rocker arm assemblies are disassembled for cleaning then the shaft end plugs must be removed before cleaning.
The rocker arms themselves must also be checked for blockages. Using a small drill bit in your fingers most sludge can be removed prior to or, between trips to the hot tank.