[L78CHEVELLE]

Here is another thing that may help some one. My car has the Ford hot water heater. When I flushed the radiator and heater box I took the heater hose from the lower radiator hose off the heater box at the firewall. I used a water hose to force water into the heater hose, which flushed the radiator and the heater box in reverse of their normal flow. I also took an air hose and blew air into the hose to provide more force in the reverse flow. You may get wet, but my results were worth it.