I broke down a 1965 273 and found an odd-looking/feeling area of bore in one cylinder. The block is standard with .004" taper. This area appears and feels rougher than the surrounding wall, almost like the iron frothed up during casting. At first, I thought it was rust pitting, but it doesn't look like any pitting I've come across, and there is no sign of standing water in any cylinder. My concern is how deep it goes and if boring will open up more of it. Looking at the outside of the cylinder through the water jacket, I see no abnormality in this area.
The machinist will have the last word on whether the cylinder will clean up at .030, .040 or require a sleeve, but I'm curious if anyone else has come across a similar type of oddity in the cylinder wall.
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