Sbm x block

yellow rose is correct that the cylinders must be round and very clean to sonic test. I've sonic tested a good many and unless they are really clean and fairly round, the readings will be inaccurate. In fact, to give you an idea of how they work, I've even tested a sleeved block before and all the sonic tester will pick up (at least the one we had) was the sleeve thickness itself and not the cylinder of the block behind the sleeve.