This may not be related to your problem but I ran into a very strange noise from the cam/valvetrain area some years back when working at the Dodge dealer. One of the techs had installed a factory crate eng and it came back about a month later with the cam wiped. The tech installed another cam and after it was running he asked me to listen to the eng with him as I was the shop foreman at the time. It had a strange growling sound in the cam/valvetrain area. I had never heard a sound like this so he installed a can of STP type additive and sent it off as everything checked ok.

Well a week or two later it came back with the cam going out again. So it gets pulled apart and cleaned again with another new cam of the same part # as the parts man just took the cam # of the old RO. Anyway when its done the tech again ask me to listen to it and it sounds like it did before with the strange growling noise and I said we cant let it go until we figure it out. Well after double checking everything we finally found out that parts gave us a roller camshaft for a flat tappet eng. It had flat tappets but they gave us the roller cam as the 318 trucks still used flat tappets that year but some cars used roller cams. That's why it was such a strange noise that we had never heard before as it was flat tappets on a roller cam. Funny thing was after looking closely at the cam after the tech pulled it back out you could tell it was a roller but not so much as you can on a race type roller. Anyway we put the right cam in it and all was well. I don't think that's your problem but it made me think of that because I had never heard a noise like this and could not put my finger on it. Lucky we found it out when double checking all the parts that went in it. Good luck with yours , Ron