[wolffcub]

If you are getting oil to the front half you know that the bolt in the block head is the right one. if the rocker assembly is old and worn out the oil will tend to favor the rear 6 rockers due to the larger clearances and not keep enough pressure in the assembly to send the oil forward. The slight lean back of the engine also exaggerates this. When at idle i get just a bit of oil from the front 6 but as soon as i rev it they get a good dose of it.

Have you had the assembly apart? If not its also possibly time to clean out the inside of the rocker shafts as the can fill with crud and get blocked. When removing and reinstalling reinstalling make sure that if your rocker shaft has a flat spot that it gets reinstalled facing the same direction.

If your setup has mechanical lifters they will always give you a slight chatter.