What happens to an engine during a cold start in sub-zero temperatures?

sis had an 81 VW diesel, smoke bomb when she started it. Governed at 55 with the A/C on. Kinda fun around town. I remembered the head gasket had ID notches in it and you had to get the identical one (or plus one if the head was milled?) when replacing or it would run with heaps of smoke. Hers was a 2 notcher and I think it as like that because she had the head reworked.