Heater hose connections...made a difference in my 1960 Windsor that went back on the road in April...when cold weather arrived, I only had heat when running slow around town...as soon as I got up on the highway, heater blew cold...engine temp was normal...coolant level oaky, etc.
I took a look in the shop manual and realized that I had hooked the heater hoses up backwards...(hey, a "loop" is a "loop", right ?)
I reversed the hoses and now have plenty of heat.
With Stovebolts, start by making sure the stat is working correctly. A 180 deg F stat is a good place to start.
Next, make sure that water is flowing through the core at a reasonable rate...with the engine warm and running, both heater hoses should feel warm to hot.
Make sure the fresh-air side of the heater core isn't choked with leaves and other compost (or rodent nests)from the fresh-air intake.
If you have good engine temp. good water flow through the core, and good air-flow through the core, then make sure that the hot air isn't being expelled through the holes for the heater-core tubes or other opportunities to escape before it gets to the heater/deforster outlets...
If a piece of cardboard in front of the radiator "magically" gives you heat out of the heater, that's an almost certain sign that your t-stat is bad...
Also, the suggestion about closing-up any holes in the coachwork is a good one...missing weatherstrip from doors or holes here and there can allow drafts that exceed the heater's capacity...
Don't cook your motor trying to get heat in the cab though...I managed to overheat my '72 a few times driving with cardboard in front of the rad !
