[whirnot]

I first flushed mine. Then when I had the head off, I jacked up the rear of the car and got everything dead level. Disconnected the radiator and pugged the inlet. Filled the block with 100% vinegar and let it sit for two weeks. Two weeks is long enough to clean about anything, try it on an old log chain. then flush real well, put it back together, and add coolant. Works well for me.......