Overheating would normally (not always, but NORMALLY) affect upper cylinders first. In most cases where #6 is rotated, it is due to over-torquing the powerhead mounting hardware (fasteners 9 and 10 as drawn in the service manual) which can distort the block casting and permit the sleeve to rotate. Those two nuts are not torqued in the final sequence (they remain at 25 lbs/ft).