well my car is in storage for winter, the other day I started it up and left it run to operating temp I revved it a few times and noticed it was shotting flames out of the exhaust, can this do anything bad?
It's probably just running a little rich from being cold, and with no cats, you're blowing more unburnt gas out the tailpipes. I wouldn't worry about it personally.
It could be a problem if its a sticking exhaust valve. But like they said you have no cats and its been sitting a while so I wouldnt worry about it too much. Now if you start getting big balls of flame shooting out, I would start worrying, lol you could burn down ur garage like previously mentioned:SNSign: