Impco vaporizers have no directional orientation on any I have. The reason any of them may say to point down is to allow any heavy ends (grease like substance) to flow into the vapor stream.
When Propane is heated, the propane vapor becomes the lightest compound and is pulled into the engine as fuel. Any heavier compounds with a higher boiling point may settle in the vaporizer. These are usually C16 and heavier, some paraffins, some polyesthers, some amine compounds, etc. Some of these products are left in during the refining process, some are leached from pumps and compressors, some are leached from hoses.
Franz
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