White smoke under heavy load is either coolant going into the combustion chamber (Lim gasket, Upper intake failure, or headgasket) or a leak under pressure (Hoses, block heater, ect).... I had a rad cap fail closed and blew my block heater out 3 times before I figured it out. I would get on it hard and next thing I knew I was making a smokescreen and the person behind me learned what dexcool smelled like.