Do those engines have valve guide seals? Is there oil in the airbox from the crank case vent tube? Have you done a compression check?
White smoke usually means oil, antifreeze makes white smoke, but it's more like steam.
Antifreeze steam usually has a sweet smell and dissipates quickly, oil smoke will have a distinct burnt oil smell and the smoke lingers around.
Gas smoke tends to be blue or black and has a strong gas smell.
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