If you look in the config.txt file of the ATSF C30-7 you'll see that there are 2 smoke containers attached to the a.exhaust attachment point.  The first one is:
smoke0
{
  texture                               <kuid2:45324:10116:1>
  attachment                            "a.exhaust0"
  mode                                  "time"
  color                                 255,128,43,220
  accel                                 0.5,0.3,0
  rate                                  15
  velocity                              2
  lifetime                              0.5
  minsize                               0.4
  maxsize                               1
  enabled                               0
}
The texture kuid is the flame.  You might try copying this smoke container to another loco to see if it works.
Bob Weber