I'm not trying to make this to elementary so as to offend anyone, just trying to explain.
The flanges I am speaking of are the ones which bolt against the head. If you take a set of Fenton headers and lay those flanges on a flat surface as they would be installed, and lay the intake manifold you are going to use with them as it would all be layed out on the engine head, you will see that the flanges of the Fenton headers are some to much thicker than the flanges on the intake - any intake. If those flanges are milled or thinned to be the same thickness as the flanges on the intake - two things happen. First, the clamps that are used to hold the headers and the intake to the head will be on a level plane as they span from one of the header flanges to one of the intake flanges. This will make for a much easier installation than if the flange of the header is thicker than the flange of the intake. It will also look correct where as with the clamp mounted crooked looks incorrect and sloppy. Second, by milling or thinning the flanges of the headers, the header's total body moves closder to the head and gives more space for the header to basically turn down quicker, thus leaving some more clearence between the header and the intake. It may not be enough space, but it will definitely amount to less grinding for the header to clear the intake. This is not applicable to all intakes. It is most prominent on the Offenhausers and the Fentons. The Edelbrocks, Thickstuns, McGurks and Edmunds seem to clear with out much of a problem. The Offenhauser is the most critical and that is the one most everopne tries to use with their Fenton header and 2 X 1 intake.
As far as anyone telling Partrick, I'll leave that up to one of you guys. I personally would rather use an original pair of Fenton headers then there are no problems.
If any of you 'Bolters have any questions, email me and I'll try to explain better or help you out.
Joe
