help annoying pop in exhaust

My first thought was a exhaust leak also...

But, I'd like to know how the valve adjustment was arrived at...meaning preload? I may be off base here, but with the slight head mill, new head gaskets (thickness) and new cam, did you measure for the proper pushrod length for this application or just use the stock one's and hope for the best.

Regardless, you may still be in spec, but I'm just curious?