I bought a snake and drilled down into the deposit. It's a good 1/2 inch deep. Acid only softens the top layer. I took a sample of the deposit and burned it with a torch. It doesn't burn, just glows. Like 51 ashton says, it's got to be chipped out but I'm not ready to pull the head off yet. By the way, I'm still green and learning (the hard way). Apparently I didn't flush the block good enough before I first ran the engine. My radiator filled with enough sunflower seeds to grow a garden. Mice just love engine blocks. Luckily a back flush got it out.

Thanks to all for your help.


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."