I've also noticed that there is considerable difference as to carb placement between different 2 × 1 manifolds.
Some (Edmunds, Tattersfield, Offenhauser) take the obvious (but may be no more than "this seems right") of centering one carb opening between the 1-2 and 3-4 ports, and the other between the 3-4 and 5-6 ports.
The other school (Fenton) places the openings father from the center, perhaps 60/40, on the basis (just guessing) that the center will draw from both, but the end pairs only from 1 and should be "favored" somewhat.
It might be interesting to compare EGT, plug temp, etc. between brands using the same carbs?
