[1965tripleblack]

I have "D" port heads for my 327, and need to know the most efficient way to shape my headers where they mate to the ports. I realize that the header MUST be larger than the head ports, but where should I put the "step" in the header...........on the floor, the ceiling, or both? The "D" port flanges that I bought are exactly the same shape as the head ports, but are 1/4" taller than the head ports. I need to know how to orient the flange in the vertical direction, which will determine where the step into the larger header will be.

[F-BIRD'88]

Make the header match or be slightly bigger, at the top of the port.

The floor of the ex port is low flow and not that critical on mismatch.

Unless some one ported the hell out of your D port heads, the D port headers should be plenty big as is.

Many people get way too carried away at the port exit. All the real gains are deep in the port.