On another note where do you find the motor likes to be timed at. I have a header, the weber setup, .030 over and a mild cam...
Just trying to get a starting point reference.
Tia

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its been 3 years since my engine froze because I forgot to drain the water.  i had a blown hg but it was just going out the exhaust so when I needed it during the day i'd put water in it and do what I needed to do then drain the water.  that one night I forgot and the temps dropped fast.  it was around 20* when I remembered and poured boiling water over the radiator and got it drained out but the freeze plugs popped out of the block.   
If I recall it did best around 12* but I would always adjust the distributor while working the throttle by hand and where ever it would take throttle without a burp then I would kill it and see if it would start easily and make micro adjustments til it started without issue.