fuel needs heat to atomize or it will fall out of suspension puddling more fuel. when the fuel falls out then the engine goes lean and you get a backfire. this is the reason OEM put a heat crossover in intake manifolds
Lot of truth in this.
Lean is the cause. If any one cylinder is lean, you will have your ignition source. Any fuel that puddles adds to the boom. You can stay with carbs, and create a vent for the path for the inevitable boom, or inject it and solve the issue. You will not likely be able to evenly distribute the fuel with carbs. Having choked carbs would help. Less air for the lean condition. Open throttle plates on start up seem like a double edge sword. Creates the lean condition, but does help vent the backfire if not to excessive.
Take any engine and start taking fuel away... even your lawnmower. It will start popping through the intake. Doesn’t matter if the engine is in perfect condition, timing is correct, engine speed, it will pop when lean. Now you take that phenomenon and add an intake with huge surface area for that pop to work against....
