No oil in top of engine

black thick goo? check oil level first then see if it has any oil pressure. then try to sort cylinders out one by one. if knock goes away on one of cylinder then that is the one to check. but, sounds like it is a serious bottom end problem.

That was my first thought. He said it made no noise when he first replaced rocker arms then after running it for a bit it started to knock. To me it sounds like a rod because of the level of noise, you can feel the knock if you touch the valve cover. I just wonder if there is any way to clean out oil passages without a complete rebuild. He was told the oil pumps rarely go out on those engines. I am a Chevrolet person so working on a Dodge is out of my comfort zone. Thanks for any advice.

I would start by changing the oil becasue it sounds like it hasn't been done in a while I hope its not to late and you have spun a rod bearing. The oil pump pick up is probably clogged and the oil pan will need to be removed.

Please let us know what happens so it will help others

Best, Ken