The stock bore was 4.125". The bore of a 406 would be 4.155"
.030"
a 400 small block Chevy has a 4.125" bore.
get a big block or bore it 54 over
4.125"
4.030
A small block Chevy has a 4inch bore. When you bore one 30 what you are doing is removing .30 thousandths from the cylinder. That would make the bore 4.030 or turn a 350cid into a 355cid.
3.740 inches
The bore and stroke.
4inch bore 3.25 stroke formula bore x bore times stroke times .7854= cid
4.156" bore with a 4" stroke.
4.155"