I figured there must be a freeze plug back there. I did do an aggressive flushing of the cooling system and probably opened up a hole. The old 216 smokes and knocks and a previous owner at one time brazed shut the breather vents at the top of the valve cover. I could probably try stop leak but the clutch is still stuck and I can't drive it anymore and resale value just dropped. I figure if I'm going to pull that motor, it will be to drop in a 235. Time to cover it with a tarp and forget about it for awhile.
