cgmach1 CG if this motor is for 1/4 racing only, then fill the block to start from the bottom to 1" below the water pump holes in the block. I would also have the block checked for trueness, and mag for other cracks. Do you have any pictures of the problem you can post. If the sleeved cracked again in the same spot, there is a problem with the boring that was done. I like Jay have never had a problem with sleeves in a block if they where machined right. Is the crack vertical or horizontal?? If the block was bored for the sleeves, I would be very surprise that the bores didn't go into a water jacket or cause a thin spot in the jacket and leak coolant or water into the block. I would start with another machinist to check out the block. We can sit here and guestamate possible problem and solutions. If you can find another FE block cheap, you are still looking at some machine work to get this one ready for racing. If you fill the block with block Crete, you do 1 side at a time. Use a sander for vibrating the Crete to remove air bubbles. give 24 hours to setup then do other side. I have seen and had problems trying to do both sides within a couple of hours of each other. Hoping for pictures. Rick L.