[GasHog396]

Have the 400 SBC block checked out before getting any parts (pistons, rings, etc.), 0.030 to 0.040 is about the safest overbore you can go if you plan on any performance upgrades in the future. If it is to remain bone stock, you may get a 0.060 overbore. There are 400's out there running a 0.060 overbore, but there a lot more that are boat anchors after the cylinder walls cracked. 400 blocks have what they call siemesed cylinder walls to strenghen the area between the cylinders, which basically means there is less metal between the cylinders, so max overbores typical on a 350 are out. 400's are more expensive to rebuild than the 350, but the added torque is worth the money. In addition, both the harmonic balancer and the flexplate (auto trans) is unique to the SBC 400, as the engine, from the factory, is externally balanced, as opposed to all other factory SBC's, which are internally balanced.

400 heads also have 'steam' holes in them. I've heard you can use 350 heads and drill out the holes using a 400 head gasket as a template. I've heard conflicting information on the necessity of the steam holes, but I guess if Chevy didn't think they were necessary, they wouldn't have put them there in the first place. These are great engines, and in stock form, don't rev up like a 350, but the increased torque is seat of the pants fun. At the worst, if the block is toast, you still have the crank to turn down to make a 383.