Technical Backfiring

When you rev a car up and it backfires is it lean or rich?

 

Typically Lean

 

Also check timing ,

Spray some combustible from a can to see if lean
Brake clean , starter fluid , mist of gas

little more information

 

I think youre right, its lean

 

what motor, intake, etc , or post pic. check couple of spark plugs

 

Lean if it backfires through the carb, either rich or an exhaust leak if it backfires from the exhaust when letting off the throttle.