Here is a pic of where i drilled the inner holes using a long series 17mm cutter Wayne at Edelbrock said i would be fine done about 4,000 street Km's just pulled it down to check couldn't find any issues 426 R3 block had to open up the push rod holes for 3/8" smith bros push rods running 18 thou all round on the crane ultra pro lifter's very quite
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