There is a very direct path on a 216 to let antifreeze into the crankcase. There is an oil line that goes from the oil distribution valve through the coolant passage in the block and out the other side under the side cover. Where the line exits the block under the side cover, the line is soldered to a fitting that is threaded into the block. If that solder joint isn't good or the line is cracked from trying to bend it into place, coolant will leak into the pan from under then side cover.
