Originally Posted by sixto

Could be something relatively simple like the typical head gasket breach into #1 cylinder. Maybe #1 has needs time to stabilize after a cold start because cold engine oil doesn't burn properly in a cold cylinder.

Could the rings be sticking when cold? Did this engine ever run on WVO or incorrect grade of engine oil? It might be worth a can of snake oil before tearing into the engine, but only as a last resort. A compression test should identify the culprit cylinder/s then a leakdown test can determine where how pressure is escaping; e.g., through the valves, head gasket, rings, etc.

Sixto
87 300D