I also remember reading about opening up an oil passage in either the head or the block to supply more oil to the cam spray rail. It is late now and I am tired, so I will look for the link to the article tomorrow.

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Well today is tomorrow. I can not find the article.

It mentioned that there is a passage, either in the block or the head, and it's cross section area is less than all the jet holes in the cam oiling tube that the passage supplies oil to. Opening it up to match the area of all the holes improved oiling to the cam and arms.