Thread: 400 ci weak?

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The 400's got a bad rap when the 4-bolt block was introduced. There was insufficient main saddle webbing strength in the block and you'd end up running over the rotating assembly if you tried to extract too much power from one. The 2-bolt block is a better choice if you're intending to use a production block.

Also, the 400's in general got a bad rap when some dunderhead bolted 350 heads onto his 400 block and it overheated because he didn't understand that you had to drill the 350 heads for steam holes to prevent overheating.
http://www.gregsengine.com/350to400.htm

I concur with Glenn about using the BBC when you intend hp levels approaching 600.

Production 400 blocks can be increased to 434, but going to a 454 small block will require using an aftermarket block.
http://www.speedomotive.com/s-86-sbchevy-400.aspx

The 383 makes a fine motor, but if you have access to a good 400 2-bolt block, that would be my choice. There's no replacement for displacement. Look at the dyno'd results of a "406 street motor" here on the AFR site. The components are listed, so it's just a "plug-and-play" situation. Look at "550 HP 406 Street Engine".
http://www.airflowresearch.com/chevy_dyno.php