Steve,
Mannel's book lists C3OZ-6303-B as the part number for HiPo cranks from '63
to '67. The early cranks were only distinguished by "1M" stamped on the
first counterweight. On some, the rear counterweight was polished,
presumably to allow for hardness (i.e., high nodularity) testing. Some later
cranks had casting numbers like C3AE-N, or may have also had an 'X' stamped
on them. Monroe's book says the HiPo crank had slightly higher nodularity
(p. 29). I didn't find anything about simply sorting out the high hardness
cranks from the standard production lot and marking them with the '1M', but
it seems probably that is what was done, as I believe you have previously
suggested. Those that passed the hardness test were assigned the HiPo part
number to distinguish them from their lesser brethren, who might be just as
hard, but just weren't tested.
Oh, BTW, my sincere thanks to Dick Barker for turning me on to this great
Ford reference book (Mannel).
Bob
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