While waiting for my msd dist to come back form repairs I had a backfire (you can not repair the E curve dists yourself-and it look like a brand new dist msd sent me back)
The rotor slip on some 30 year old dual point I was using but right by my house, yeah it was loud and the motor then shut off. That was last summer and all is still fine. I'm sure all my neighbors heard it, lol
Watch some of the old 60's Munsters reruns, that old hot rod car they used loved to backfire.
Now I would not be surprise if backfiring can cause major damage.....I think there is safe backfiring and unsafe
I know a crack header pipe will cause loud backfiring noises on deceleration, give it a bit of gas it stop, let up and bang bang if its in a low gear or running steep gears in back...I ran it for a month or two like that until the weather warmed up and too many people outside would jump and look--think it sounded a bit like gun fire--but the sound doesn't carry--suburban folks don't know the difference