chevy starters usually come with shims, and a little narrow rod that is actuly a gap guage for measuring starter placement,
cracked cone, sounds like it was installed with out shims to correctly space the starter from the "bell housing", this puts stress on the starter when the starter gear engages the ring gear and is forced sideways
this can also damage the 'flex plate' that holds the ring gear
i had one chevy 454 with a cracked and repaired bell housing that was not 'true'
everything was under stress, 3 starters and 1 flex plate were replaced, before the problem was found
this info does not apply if you have a dodge 440
I can explain it to you.
But I Can Not understand it for you !
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