There are all kinds of flames from the exhaust, as has been mentioned!
You can get it "honestly" like on race cars where the engine is set up rich enough on the low load fuel control (carb or FI) so that there's enough unburned fuel in the exhaust to ignite when it finds O2 in the atmosphere;
you can get it by cheating with kits that are offered now that give you a switch to push and it cuts out your ignition for a second and at the same time starts pulsing a spark plug in your exhaust tip;
or you can do it UP and inject your favorite witches brew (often involving kerosene & gas) into your exhaust just in front of the spark plug(s) you've got mounted out there! Then you can enter contests and shoot 30 foot flames!