I have a Gen 6 block non Siamese cyl walls and I sonic checked it today. I am considering boring it big. + .125 over. My flatlander kit with a +.250 4340 crank should be here before Christmas. In the block that I have the cylinder bores are centered and the thinnest spot between the bores is .179. My question is this. If it is totally acceptable to bore a block +.060. It would make the thinnest spot between the cylinders at .149 thick. I know this is not the trust surface of the piston travel. In the area the area on the outside center of the bore the thinnest spot that I have is .267. With a standard bore. Most of the outer thrust surfaces are over .310 inch or so. If I take it to +.060 I would be making the thinnest part of the cylinder with the most pressure from the rotating assembly at .233. I have heard that the thinnest point on the trust surface should be a minimum of .200 inch. Is this a good thickness? If so could I conceivably bore the stock gen6 block that I have to +.125 and still have only .205 inch for thickness on the area of the cylinder that takes the most abuse. . Being that in a marine application the blocks run cooler and the pistons run hotter so we have to give them more clearance for thermal expansion, is the +.125 bore that gives you .205 plus or minus on the trust surface going to give you enough strength? Is the then thinnest part of the water jacket between the cylinders .117 going to be too thin? I would like to unshroud the valves as much as possible but I do not have the money for a Siamese block this year. I am buying AFR heads I purchased the boat this year. I dd2000 the engine combo and it should be around 590 hp NA Plus or minus a few HP