I had an interesting experience with the 617.

I'm in the process of redoing the head. The radiator was drained, the thermostat housing was completely removed.

I'm staring at the return hose to the water pump. The hose is filled with coolant. So, the 617 is filled up to level of the head (lower part) after you have fully drained the radiator.

Got underneath and removed the block plug. About 3 quarts of coolant headed out of the block in short order.

There is no possible way of changing the coolant properly on the 617 without removing the block plug.