Nothing much beats boiling a block in a strong solution of water, laundry detergent, and lye. I have used a cutoff wheel on an angle grinder to split a 55 gallon oil drum in half vertically, and build a support structure from pipe fittings to hold the half drum about a foot off the ground. Fill the drum with water, add a small box of Tide and a gallon of Sodium Hydroxide "main line" drain cleaner. Submerge the block and build a fire under the drum. After a few hours of boiling, remove the block, cylinder head, oil pan, valve cover, and other cast iron or steel parts (NEVER ALUMINUM!) and give them a good rinse with a pressure washer. Once the parts are clean, they will flash rust almost immediately, so apply a light mist of oil with a spritz bottle as soon as they're dry.
Jerry
