As an example of tuning dual quads:
I figured the effective metering area at WOT for Carter 4345s and 4346s used on the Chrysler hemi. Remember for Carter carbs, the effective metering area is the area of the jet less the dynamic area of the rod. At WOT, this would be the power tip. These are FACTORY calibrations.
4345s (front carb)
Driver side primary 4.18E-3 sq in.
Passenger side primary 4.43E-3 sq in.
Driver side secondary 4.66E-3 sq in.
Passenger side secondary 5.41E-3 sq in.
4346s (rear carb)
Driver side primary 6.42E-3 sq in.
Passenger side secondary (also) 6.42E-3 sq in.
Driver side secondary 4.30E-3 sq in.
Passenger side secondary 3.63E-3 sq in.
3.63E-3 is "shorthand" for 0.00363
Is it necessary to go to this extent to make the dual quads work? No, but if you want the maximum effect from the dual quads, then yes.
Using "normal" jetting where the step-up rods (a.k.a. metering rods) are the same, all four primary jets the same, and all four secondary jets the same would probably cost in the vacinity of 10~12 percent HP. 10 percent on a 400 HP engine would be 40 HP.
For the enthusiast that is a "driver only" the single quad is probably the best way to go; but for the enthusiast that enjoys tuning, there IS more HP in dual quads than in a single.
Jon.
