340 block value?

nm9stheham said

But also more leverage on the 360 crank from the longer throws... I guess that's what drove the larger main journal size.

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The larger main journals was to increase the Rod throw overlap because the crank was cast steel and not forged steel.

That's why all the Buick, Olds and Pontiac stuff had comparatively large main diameters. They all had fairly long strokes and cast cranks.