Sonic checkers

The scale on the inside of the cooling jackets? It does make a difference. I try no to do a sonic test until the block has been thru the airless shot. It get's rid of the scale. Hot tanking/boiling doesnt even get all the sand out some times. What I find is it tends to test thicker. But that could also be part of the casing action too. Really, the areas that will crack are well above that seam. I test strting from the point where the readings go from way thick to what I would expect. That ends up in most blocks to be about 1-1.5" up from the bottom of the bore. The issues from the scale are below that usually, if I run into them at all. If the sonic test is the first thing you do, you will get more erroneous readings as opposed to after the main cleaning has been done. Typically guys want an answer before they spend any money to clean. I discourage that.