The 400SB did have some problems related to heat and the Siamese cylinder construction compounded the problems. There are some fixes that work (as simple as a 3/8" hole to very elaborate machine shop work) but many people believe that starting with a 350 4 bolt is the best way to make a lot of power in the small block Chevy world.

World Products (and others) market a 427 CI small block (4.125 bore x 4" stroke) that produces well in excess of 550 horsepower with 525 F/P of torque - it's spendy, but some folks want to have the small block look.

If you want lots of thump - talk to Pat about a big block Chevy. He's the master and has forgotten more than most of us will know about building bullet proof big blocks with a reasonable outlay of cash (remember - you usually get what you pay for)..

Regards,
Glenn