You're sure the block plug is working aren't you? You have good cranking speed? The engine oughta be warm after 36 hours. I would bring the battery inside and let it warm up for a few hours - that is going to get it warmer than the charger will I think.
I concur about valve adjustment, not like you are going to do it in the present conditions, but if you are out of spec adjustment will help a bunch. You want the cylinder to be as full as possible when it starts to compress, so it can create maximum heat at full compression. If your valves are off you are either closing them early and not sucking in as much air as you could, or you closing late and are blowing air out that should remain in the cylinder.

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andy t
'78 300d
'95 volvo 850, wagon
'86 300sdl - engine out, maybe I'll have it rolling by June

whole bunch o' bicycles