I have a 1990 Honda civic si. After making one stop to drop my daughter off at school. I started the car and a huge amount of whit smoke cameout the exhaust, The car was running rough and sluggish as I hoped it would stop and I could make it back to the house. NO LUCK!! The car started to overheat. I think it is probably the head gasket or blown cylinder head. Just need a little more help on the problem before I tear it apart and fix it. ANY THOUGHTS? I would appreciate it. Thanks