[chevyrestoguy]

I love them. The whole notion about them overheating is an old wive's tale. There are few differences in the blocks, however. The -511 blocks are the 4-bolt blocks, and believe it or not, they are the weakest of the bunch. They still make a great street engine, but if you're really stepping on them with nitrous, they have a limit (over 500 horsepower) where they can become a problem. The -509 and -817 blocks are the 2-bolt blocks and they are the desired block, especially if you have them drilled for the aftermarket splayed main caps. I wouldn't suggest anything over a .040 overbore because of the siamesed bores, and also because the 400 blocks are notorious for core shift.

Build it, you'll love it.