Brian,
You are absolutely correct. Just goes to prove that Pontiac guys are some of the smartest guys around.
We did do our flow numbers with a 4.35 I believe it was.
If you take a Pontiac cast iron head, like my 455SD block that I run in super stock, and put the OEM SD head on it, and look up the bore hole backwards, it will frighten you to death!!
It makes the valve shrouding issue very apparent. This is with a 4.215 bore and a 2.11 Valve. The Pontiac engineers were smart about notching the blocks for valve flow.
Our next step is to go to 4.223 on the Super STock stuff. The Chevies are ahead of us on this one because they found out a long time ago that the SBC with a 1.88 intake doesnt run that much slower than the 1.94.
With the Wenzler heads it is exponetially exacerbated by the valve spacing when you try to go to the larger intake valve. So we have redone the valve spacing.
Even with all of these techniques, it still requires a 4.40 bore (my opinion)
We also are looking at head placement to maximize those shrouding issues.
When we take the next step to the 2.40 valve, it will be very interesting if it can be done at all. We are still working on it.