Many people have the belief that the oiling problems to the rocker arms is a result of the cam bearings having been installed wrong, or they have rotated out of alignment, blocking the oil passage holes.
It has been my personal experience that there are two culprits, one is inferior grades of oil, and/or a lack of regular servicing. The second problem is the design of the 292 oiling system. The oil passages come up through the center of the block, it then makes a right angle turn across the block for about an inch, lining up with the oil passage in the head (s) which aligning with the center rocker shaft mount.. The oil is distributed through the shaft to each rocker arm, a portion of the oil feeds through the rockers, running down the push rods to the lifters.. Another portion of the oil is returned to the engine via a tube, one on the front of one head, the other on the rear of the other head. The front tube lubricates the timing chain/gears, the rear tube lubricates the distributor shaft/gears..
The use of non-detergent oil in a Y-block will cause the small passage across the top of the block to plug up... No oil or a very reduced amount will get to the valve train, etc.
The common solution to this problem was to put an external oiling system on the engine via a small tube coming out of the block oil gallery, up to hollow rocker arm studs that held the valve covers on..
I had a '59 F100 in about 1971 that was not getting oil to the valve train. I was told to put an external system on the heads. When I pulled the valve covers to install the hollow studs I noted the extreme amount of sludge in the rocker arm area. At first I started to wash the sludge away, figuring I could flush the crud down into the pan, then drain it out..It became apparent to me that the rocker arms were worn out, I removed them, which revealed the the oil passage hole in the head was plugged. I tried to clear the hole with a wire, the wire would only go about an 1-1/2" and stop, I pulled the heads, finding the blocked passage in the block.
I cleaned every thing out, re-installed the heads, installed rebuilt shafts and rocker arms, installed the valve covers, new Castrol GTX 20/50 and drove the truck for several years..