head casting number 4772576?

Rumble,
When bowl blending is done and a good valve job also the #'s can increase greatly like 20-40 cfm's, then add gasket matching to this and the heads should flow very well. The thing is that these heads have a very large short turn in them, which makes the low lift flows really come on, then stall, which is what happened.
Also looking at it from the factory's stand point is that they the factory didn't install cams larger than .500 lift so anything over this wasn't of concern to them.