The 400 is not a big block rotating assembly in a smallblock case, it's really a criiter unto itself. Originally introduced as a passenger car emmisiions engine. Crank is cast, not forged like the 350.
I can understand your frustration, but the 350 is an extremely reliable and very well performing engine. There's more 350s out there than any other engine ever made. They've powered everything from hi performance Corvettes (no 400 in a 'Vette) to police and taxi cabs. I've seen police versions go well beyond 200k miles without an overhaul, just regular maintanance. Seems to me that you may have gotten dud engines, probably not assembled properly to begine with, rather than it being a 350 as the problem.
