Hy 1965 Chevy C10, congradulations on your engine rebuild. Your white smoke may not be smoke at all, but rather steam. Do you know how the engine ran before you rebuilt it, or putting it another way do you know why the engine needed to be rebuilt? A rebuilt engine will smoke until assembly lubricants in the bores and combustion chambers "burn" off, that smoke is blue in colour. Black smoke indicates an over rich [too much fuel] situation. So your "white" smoke may not be smoke but steam, did you have the block and head pressure checked for coolant leaks during the rebuild?
