Pop pop on exhaust side

Hi, just trying to fine tune a 360 with about 10.5 compression. Iron J heads 2.02 . Medium cam lunati 703.

I get a pop pop at random in the exhaust.

I have the timing set around 18 degrees intial.
It doesn't seem to matter where I advance or retard it too. I get a random pop pop normally I run around 12-15 initial and then another 18 or so all in. Mechanical billet msd distributor and 6a box. Msd blaster coil.

I wonder if it doesn't like my autolite 65 plugs if I should step down. ?

I lean out or enriched the carb and I still get the same problems

I have checked all my spark plug wires

I'm running out of ideas , my plugs look good still if hasn't run much or hit the street yet

Thanks