He probably didn't check the piston skirt clearance properly when he installed the 235 pistons. The 216 block has to be bored .060" oversize and the cylinders have to be honed for the proper fit. I bore the cylinders to the exact size of the bigger pistons, and hone for the proper clearance, usually about .0015"-.002" The "216" ends up with 224 cubic inches when std. bore 235 pistons are installed.
Jerry

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