7 1/4 why weak?

I had several 7 1/4 in A bodies, that had whin. I never actually broke one, but then again I didn't beat on them. granted they probably had many ( maybe several huindred miles~!???). it is unusual to find a Mopar mechanical part from back in the 60's that was weak.
back 10 years ago, an A body 8 3/4 was not scarce or expensive! you know the 8 3/4 was strong as it was standard on auto hemi cars! I've had a couple of A cars with 8 1/4 and had no trouble with those but then again I ain't a racer! can only afford to build it once!!! LOL