I also had my car out last week on 12/29 and 12/30. Weather was perfect both days. I had the same problem as you, couldn't get the
oil temp to get up past 40c until I had the car sit and idle for 10 minutes. Afterwards it took me 30 minutes to clean out the carbs. Webers don't like idling in the cold, or at least mine do not.
Weather is supposed to be cold but very nice this weekend, going to try it again. The car just looks soooooo lonely sitting in the garage a is just begging for attention.
jim