Steam Holes in a SB 400
 

Longhorn Man mentioned something about steam holes in the Stroker vs. 400 thread. What are they, what do they do, where do they go, and do you really need them?

:bowtie:

they are between the cylinders on the deck surface. yes you need them if your going to use the motor on the street. the 400 blocks have symiese cylinders and if i remeber correctly, coolant doesn`t flow between the cylinders like it does in a 350 block. i can`t remeber if water actually goes through the steam hole but it keeps the cylinders from over heating by letting the steam out of the area. someone else might have a better way to explain it to you but unless your useing the motor for drag strip use only, you need them and the have to be drilled at a certain angle. most machine shops can do this for $50-$75 depending on the shop.

Nothing to drilling the steam holes. Use a gasket as a template and drill away. There are six holes per head (two between each cylinder). The holes are 1/8". The holes on the intake side are 30 degrees. The three remaining holes are straight.

Hope this helps.

The Chevy Power Manual (about $15 from GM) has instructions for drilling the holes.

They're called steam holes because their purpose is to eliminate steam building up in the water jacket. Steam doesn't transfer heat as efficiently as liquid coolant. The steam holes make sure the liquid keeps flowing.