Exhaust backfiring issue help

I am still having an issue with my 440 backfiring through the exhaust.

I changed the cap, rotor, wires, plugs, and also rebuilt the carb. The engine has been rebuilt and has not seen any usage. The exhaust manifold gaskets are brand new.

Any advice on where to start?

Is it a hyd cam.. but either way.. could have a
exhaust valve open a little... or is it back firing
a lot(like all the exhaust valves)... I assume the
timing is correct

I believe that is caused by a rich condition

A consistant backfire or random pop?

Yes next step is adjusting the valves. I played with the timing and no luck. It is random poping.

post a picture of all 8 plugs in a row.

I had the same issue a while back. Went thru ignition and carb without finding a cure. Finally pulled my gas tank, drained it, filled with fresh gas and my popping went away. The new formulations of gas do not last long. I always used premium but it is oxygenated gas in AZ.

I moved to WI and the premium no longer has ethanol. Seems odd that they grow tons of corn here but don't add ethanol to all the gas like they do in the desert!

Good luck finding your issue.