Have not got a clue what would cause this. I have been measuring, calculating, change and re-checking this block for 2 1/2 weeks trying to get the crankshaft to turn in a block that by all calculations should have had 2 1/2 thousandths clearance. When the crank and mains were first installed and "plasigage" was used it measured 2 1/2 thousandths. Problem is the crankshaft will not turn. Took everything, including the block, to a machine shop this morning. Crankshaft was re-checked, bearings were re-measured and then we go to the block as I said previously when we measured vertically we were back to square one that should have been perfect. Measured horizontally in the block, slightly less clearance, but it still would have clearance and should turn. Measured diagonally and the block was .005 less than the other two directions. Mains do have studs; however, the caps slip down easily and will lock in place with just pressure from the palm of your hand. To clean this up means I need to get 2 1/2 thousandths on each side on the diagonal.