[77newell]

On my 6v92 white smoke is unburned fuel. Two things have caused it, cold engine as Ernie noted or a poorly atomizing injector or both to some degree. One thing to try; start it and let it run until the smoke stops or diminished noticeably and not a second longer. The check the temperatures of the the exhaust ports of the individual cylinders. If one or more are consistently cooler through several trials with time between to let everything cool, then you know it's either injectors (not cheap) or cylinders going bad (even more not cheap). I suspect that it is injectors since you noted burps occasionally when driving and the engine presumably hot, I doubt bad cylinders would give you that symptom.

jon
77 Coach