Thinking over all your complaints about excessive coolant
overflow, "white smoke," low compression in two cylinders,
it's beginning to sound like you have a head gasket problem
between a water passage and a cylinder. Do you have any
water in the oil? It would probably look like thick brown
foam.
Get your car to a good mechanic, not the bozo who sold you
the shiny GM alternator, and have the cooling system
pressure tested.
Why on earth would you want a "water filter?" You car
doesn't need Perrier.
--Roger van Hoy, '55DeSoto, '42DeSoto, '66Plymouth,
'73Duster, '81 Imperial, Washougal, WA