Water pump impeller clearance question

The manual is CORRECT in stating the impeller should protrude 0.007-0.017" BEYOND the gasket face of the pump casting, so that when the gasket is between the pump and the back plate the clearance between the impeller and the back plate will be about 0.023-0.013" when bolted to the engine block ( the gasket will compress some). I put one of the China pumpd from Kanter (Rebuider's Choice) on a 51 Hornet, and it would run hot at idle and low speed......the 0.080" clearance on the China made pumps is excessive, allowing high pressure coolant to cross back over to the low pressure side, thus reducing the pump pressure in the block...... The higher the pressure in the block, the higher the boiling point........when pressure is too low in the block, hot spots start creating vapor pockets or bubbles that reduce heat transfer.....the vapor pocket grow in size, forcing coolan t to flow out the over flow tube on radiator and the cylinder head temperature climbs. I took the China pump out and put a rebuilt pump with the correct 0.017" protruding pimpeller and about 0.013 impeller to back plate clearance , and the 51 Hornet ran cooler without blowing off coolant at idle and low speeds.

There is NO discrepancy on the clearance in the Hudson manuals.....I t exists only in writeups you may have seen written by other people.....Have no idea where they came up with such a huge clearance for the impeller to back plate, if indeed that is what they were referring to. I never seen that reference you mention anywhere.