Pull the draincock in the driver's side of the block. I'm wagering you'll find a lot of rusty crud. If that's the case you'll have some work ahead of you. Proper coolant contains rust inhibitors that help keep the metal parts of the engine from rusting. In the day a lot of folks didn't change the coolant or even ran just water so, over time, the block & radiator fill full of rust. Rust doesn't transfer heat well plus it blocks the proper flow of the coolant.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.