it appears the width of the 454 GM TB is wider than the top plenum of my weiand single plane manifold? this i determined from the gasket for squarebore carb to intake top. seems the intake will protrude about 3/16 on each side on sides of venturi's of TB's. so air flow will hit that ridge and rool over it. the adapter(howell) is exactly sized for GM TB so no taper. maybe no big deal as it is only an eliptcal quarter moon shaped area. anyone else see this? TB not yet installed and i am inspecting units in box not on car.

 

This is a common problem with carbs and TBI's and you can have that lip machined down so that it tapers into the manifold. It may also interfere with the blades from opening all the way in your TBI unit. So it is a good idea to get that taken care of.

 

even with the 1/2 inch adapter plate in place it will interfere? if i dremel out the top of the intake i will lose valuable mating surface and potential vac leaks result. the surface of the intake top already is machined down about 1/4 inch to add clearance for hood. i am concerned the intake casting is also thin at top of plenum. any futher comments? yikes did not expect this.

 

Shouldn't hurt; I had to bevel the edges of the manifold opening and I had no problems.

You've got it easy. Imagine doing it with 2.2" bores