I was talking with someone about a 446 build that was on the dyno yesterday.
We were discussing the actual compression ratio because we had come up with different numbers.
Well, apparently KB has made some changes to the designs of several of their pistons in recent years, and after my catalog was printed.
In the case of the 446 in question, the flat top piston #237 has gone from a 6cc valve pocket to a 9cc valve pocket.
On this motor that equates to a .3 difference in compression ratio.

I went on line to see if the same was true for the 383 pistons, and it would appear it is.
The old KB 400 domed piston in my catalog has a pretty big dome and works out to a 6cc effective done volume.
The new KB 400 has a noticeably smaller dome, and now has the effective dome volume listed as 0cc.

In light of the new configuration of this piston, I agree with JohnRR in that these are not really a preferred choice anymore.

I don't really understand why KB wouldn't somehow differentiate the new versions from the old, since they are obviously not the same any longer.

Just thought I'd pass that along.