340s I had a set of comp Magnum rockers like you have there and also used their pushrods and at first the pushrods I had were a little too long so I had to back the adjuster out to where only about 1 thread was showing so as to not have too much lifter preload and it was real noisy like yours. I found what was happening was the pushrod cup on top was contacting the rocker arm at full lift. I swapped the pushrods for shorter ones so then I had about 2-1/2 threads on the adjuster showing and the noise left because the pushrod cup no longer hit. You might have a look at that.