[skid]

The 400 small block will make more torque than a 396 big block, and the big block will make more horsepower with all things being equal (cam, compression, carb., etc.). The reason for this is in the heads. The s/b has smaller heads which have more velocity which is good for low end torque. The big block ports are much larger, which is better for higher rpm and hp.

I dug into the archives (Chevy High Performance 1999) 7 best engine combo edition where they have similar built s/b 406 vs. 408 rat. Small block best torque was 509 @ 4000 vs. big block 465 @ 5000. Horsepower was s/b 452@5300 vs. b/b 480@6000. Estimated 1/4 mile for the same car was s/b 12.29@114.1 vs. B/B 12.21@116, so the big block would be a fender length ahead. However the small block would be a slightly better driver/tower due to its better low end torque. But the difference would be small.

Really, a big block vs. a small block of the same size and spec's will be very equal. I have a 480 hp/500 torque 406 small block motor in my Vette (with a very mild 222 intake duration @ .050" camshaft), and there are not too many street big blocks that can out run me, least 'round where I live.