Thread: Tell me about a 400 sb

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Originally Posted by 53 Chevy5

Are these things any good?

Yes, great motor. I think that part of the overheating legend is using heads other than original 400 heads on the block that lack the extra cooling holes that a 400 came with originally. That and/or maybe using a 350 head gasket instead of the obligatory 400 gasket with steam holes. Unlike any other Gen I SBC, the 400 cylinders are siamezed into the crankcase, so that cooling water does not flow all the way around the cylinders. This leaves some dead ends where the water can be superheated and turn to steam, blowing the head gasket, if the steam is not relieved. Here's a tutorial for drilling steam holes into heads from a 350, for instance.

Chevrolet used a shorter connecting rod in these motors, 5.565" instead of 5.7", so you want to be aware of that when rebuilding. Most fellows will opt for the 5.7" 350 rod when rebuilding, but then you must grind on the rod shank for clearance between the rod and a few of the cam lobes. Companies such as Scat sell rods that are clearanced from the factory, a much better idea than grinding on a stressed part, in my opinion. Look at Scat Pro Stock rods.

Technical Articles at Greg's Engine & Machine

Add up the parts of your stack when building a 400 and pay attention to the compression height of the piston that you use.

Originally Posted by 53 Chevy5

Why don't people use them more rather than building 383's.

Scarcity. Most of them have been found and used by now and are in the possession of a hot rodder or circle track racer somewhere.
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