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It sounds like you are missing the hot air stove that wraps around the exhaust manifold above the water pump. It is an aluminum casting with adjustable openings in the end that allow warm air to be drawn through the opening in the block you describe between cylinders 3 & 4 into the back side of the carburetor on the other side of the engine.
The tube that passes through this opening carries water from the water pump to the carburetor. The carburetor is designed to allow warm water to circulate around the outer part of the carburetor, then up through the intake manifold, and back into the block. There should be a shut-off cock on the water-pump side of the tube. You should also find a drain-cock on the carburetor to drain the water out of the carb’s water jacket.
The engine of my unrestored Series 33 is black.