Re: 400 SBC opinions
Are you planning on using a closed cooling system? If not, don't do it.
The steam ports will quickly become packed with rust/scale (especially salt water), and localized overheating will begin.
The 400 is an example of trying to fit 10 lbs of s**t in a 7 lb bag, on a budget. GM didn't do a stellar job with designing the cooling system, and things quickly turn south when those little bitty ports plug up.
IMHO, you would be better served building a 383 stroker. You wouldn't be using a rare block that's A. Getting harder to find, B. Has the above mentioned cooling issue, and C. Is prone to main web cracking (if using a 4 bolt block).
If really want a 400, you would be best served getting an aftermarket produced 4.125 bore block. All the issues are resolved, and you can get them in many different flavors (such as a medium journal sized mains). You would also be working with a NEW block instead of something that's 30 plus years old, and needs a bunch of machine work.
