Honing with Torque Plates - How Important?

On a small block the difference is about .0003-.0015 depending on the position you measure when you check the finished bore diameter near the head bolt holes without a head in place. The problem with not using the plate is the top of the bore where the rings are sealing has the highest pressures. That change in bore wall shape in that area can make it impossible for the rings to properly seal near the bolts. The distortion can also be simulated using some spacers and the same fasteners you're using for the heads, plus the same type of gasket. The load of the fastener will deform the iron around it. Remember the block is not a solid casting. It's hollow. So as you pull or distort one spot, the adjacent areas deform as well. The amount of deformation depends on the material, the fastener, and the load. Big blocks don't deform as much because they have 5 head bolts per hole and are torqued at 10 foot pounds less. So the load is more evenly distributed around the bore. Small blocks move a lot IMO.