I very slowly drilled the drain hole till I touched the casting then stopped. No luck. It's still plugged up. I've taken a hard wire and picked out as much as I can. I picked a passage going left at the back of the drain hole but it stops after about a 1/2 inch. It feels like casting at that point. My guess is that the passage goes up to get to the water jacket but my pick will not go up that far because of the angles. I removed the water pump but I can't see to the back of the block. There is no way around #1 cylinder. I have to clean what I can from the rear freeze plug hole. I put a little of the black stuff in a plastic container and poured in a little muriatic acid. It does not react like metal (fizz and bubble).
