Be sure and visit the "Shortfalls of Model A Water Pumps" page for information on the poor design of the stock Model A Ford water pump.  Then don't miss the pages for my leakless water pumps.  I have included pictures of cutaways of my pumps so that you can see what makes them leakless- and so much improved over the "Ford" original design.  I now have a new design (Extreme Duty) that is truly remarkable; there are sealed ball bearings at both the front and rear of the pump.  This pump was designed to withstand the severe loads caused by the extreme belt tension used with alternators.