Yes. No problem doing that. Is the engine on a stand?
You can use a pressure washer to get all the way in there to blast out the loose crud. Evaporust, CLR, and other , similar products do a great job cleaning out a crudded up engine.
Run a thread tap through the hole before putting the plug back in.
You can also knock out all the core plugs to gain access to help clean the block. They can be replaced with rubber expansion plugs if you don't want to pound brass ones back in.
