[Adger Smith]

Billy, My buddies at Brodix tell me that as their Core boxes wear the port is cast smaller.
I was questioning them one day about their advertisement for port size and flow. I told them that what I buy never matches the advertised size and flow.
Dave Roder told me it was because all the ads are done off the first production run and as they pour/cast more heads the ports get smaller.
I'm no foundry expert so I just shut up and accepted the explanation.
Probably what they wanted me to do, LoL.
I would bet that the GM X means the mold/core box was modified. If the X was for worn out why would they be using them? No doubt the X castings I've seen always seem to have more intake volume.