Shake Shake Shake

Sorry I see you said comp rockers so I'll assume they are the stamped 340 style. I have to agree with Brian6pac the valves sound WAY OUT of adj. or you have very low oil pressure at idle. Have you pulled the valve covers and checked anything? Look and see if all the pushrods look ok, you can just crank it and look. Also check to see if any are protruding thru the rockers.
I just had the heads off, and everything looks great. Rockers, pushrods etc. When I made the video, I should have walked around back, because the valves don't sound out, nor does it sound like there's a misfire. Idles really nice. The sound in the video is not a good representation of reality. Actually it sounds like hell in the video. Haha.