What might cause white smoke from the exhaust after having a head gasket repair done?

Having a CRACKED head will make WHITE smoke IF U didn't have the head MAGNA-FLUXED. White smoke is steam. if it doesnt quit after awhile Id say that there is a leak in the head gasket between one of the coolent passages and a cylinder. this will let water into the cylinder which is turned into steam during combustion then exausted out the tail pipe. just to clear up something: Magnafluxing will not prevent cracks, it is a process used to detect them. This should be done by a machine shop. the new gasket is obviously faulty, or the head is cracked. I would guess that its the gasket. The head may not have been torqued properly. Follow a Chiltons or similar repair manual very closely when installing a head. If this is immediately after getting it fixed, you have to give it some time to work all that coolant out of the exhaust system. If it still is blowing steam after a few miles, then probably you have another blown headgasket or a cracked head that should have been addressed on the first head gasket replacement. Some shops have been known to not verify that the head isn't warped or cracked, and if it is, the new head gasket will blow immediately. If you had it at a shop the first time, take it back to them and have them fix it right this time - remember, though, not all mechanics are created equal and if they don't make things right you should take this to a better shop. A good shop will be embarassed by such a rookie mistake and take care of you. It is also possible that the head is warped (repair by machining) or that the intake gasket is or was also leaking or warped. Warpage typically only occurs if serious overheating occurred or sometimes if the wrong torque sequence was used during installation.