A friend of mine had a pretty severe backfire in his stang years ago and it did lots of damage. A solenoid hung open in the shutdown area and it died, so he went to fire it up on the return road and BOOM. Hood, intake, throttle body, ring lands on the pistons were all done for.

I have done the same thing as you have, but mine bent the primary blades and I never could get it to idle right again so I had to get a new baseplate.