White smoke in your exhaust smoke would imply burning brake line oil that is probably entering the intake from a busted one-way vacuum valve to your master cylinder. Highly improbable, but it does happen. You tend to notice this when your brakes stop working...

Black smoke = overfuelling (carbon)
Blue smoke = Oil burning
Steam = possibly normal moisture, accompanied by dripping exhaust
Steam plus brackish smell = possible burst head gasket (burning glycol coolant - check the radiator and oil)
White smoke = hydraulic brake oil

One of the few remaining Mk1 owners... #00015