I figured as much. I had read another thread and people were saying that water will overheat the engine but in reality, water cools better than antifreeze, and the anti-freezes job is to raise the boiling point of water and prevent it from, y'know, freezing, and protect against oxidation. I just didn't know if it was a good thing to do in an engine like this.
I know my grandpa used to drain the radiator every night in the winter because he couldn't afford antifreeze in his old truck, but that was an engine that was made before antifreeze was made available for everyone to use, so I didn't know if this engine was any different
You are so confused.
There is nothing wrong with using straight water for a few days, or even weeks, the issue with water comes from the long term. Water and iron rust, rust clogs the passages, and THIS is a problem. Water also does a chemical reaction with the aluminum head that becomes a problem in the long term. If you do repairs to the cooling system and want to test using water from the hose attached to the front of your house, go for it. Don't leave it in forever, but there's absolutely no problem with driving to work for a week to see if your repairs will hold. Of course, climate conditions present their own special considerations, and I live in San Diego so I never experience those conditions, if you live in North Dakota (or Texas if the news is any indication) you could experience the conditions before the water gets from one end of the hose to the other.
Antifreeze lowers the freezing point of water (water must get colder before it will freeze), it also raises the boiling point (water must get hotter before it will boil). It's also an anti-corrosive that helps protect the metals in the engine.
Grandpa drained the block to keep the water from freezing inside of the engine and pushing out the Freeze Plugs that are designed to fall out when the frozen water expands inside if the block. The Sears Catalog, and others, once had heaters that would cycle the water and keep it hot overnight. They came up with several strategies to keep the water inside of an engine from freezing, I would not be surprised if they still had markets where engine heaters were popular.