I found a 400 sbc. The guy says the block is good will need to be bored. What exactly does that mean? Is that like grinding shavings off? how much does this usually cost?

 

Wow you have a lot of learning to do. Go to a book store and get a book on the basics of small block chevy's. That will help you alot.

And to anwser your question boring a block refers to enlarging the bores to provide a clean, smooth surface for the piston rings to ride on. How much does it cost? Call a machine shop and find out.

 

before you buy the block from this guy, have somebody who knows engines look at the block so you don't get taken. The price will differ from shop to shop on boring, you will probably need more than that, though. Probably would be a good idea to rebuild it while it's apart for boring.

 

I agree that you should have the block checked out. 400's should not be bored over .040" oversize and if it has four bolt main caps, it probably should be magnafluxed (a process for checking cracks) before you spend any money building it.

 

I've never heard that. What is the reasoning? I'm wondering because my 400 is already bored .040 over and I was hoping I could take it to .060 over when it needs rebuilding in the future. They do sell .060 over kits, so obviously people do it.

 

400 blocks have alot of variance and core shift. Some blocks are good to .120 over (don't think you will get lucky enough to find one like that though)... on most the walls get thin at .030 over. You deff. need to have the block sonic checked if you go more than .030 over.

 

Fbird84,
400's can be bored +.040 after they've been sonic checked (firsthand experience). That experience also taught me that if your going to build a 400, get your core from the machine shop you plan to do buisness with. My "pet" 400 block required an additional +.010 which required expensive "custom" +.040 pistons.

Long story short, it's actually cheaper to source your block from the machine shop that your gonna get your machine work done. You get a known core where all the checking is already done. Believe me, there are people that will tell you anything to get rid of their junk.

Anyway you slice it, the 400 sb is expensive to build. Have fun though, and be careful!

rattlehead

 

Because of the large bore, the cylinder walls are thinner than other SBC's. Remember, the large 400 bores fit within the confines of basically the same dimensions as the rest of the SBC family. Something had to go. In this case, cylinder thickness was compromised. I'm running a .060" 400 in my truck. I used a street fill of Hard Blok block filler to stabilize the cylinders. This motor never sees the other side of 4500 rpm. It does fine for it's intended use but I wouldn't do it again if this motor was going in my IROC where my driving is more aggressive.