Each top is completely divided in half. There are two tops, each of which has completely separated right and left plenums. So there are four plenums all together. Using small-block Chevy cyinder numbering, there is one plenum for #1 & #3, one for #2 & #4, one for #5 & #7, and one for #6 & #8.
When you start thinking about the firing order, you quickly see a big problem we had to engineer around. #5 and #7 fire right next to each other in the firing order. The other pairs have a pattern like bang-rest-rest-bang-rest-rest-rest-rest (for #1 & #3). So you get this weird induction, rest-two-cycles, induction, rest-four-cycles pattern. For some pairs the cylinder under the primary venturi goes after four rest cycles, while for the #6 & #8 pair it is the cylinder under the secondary. So we had to do some major work on the carburetors to get even fueling everywhere. We have screw-in air bleeds, and each venturi has jetting and air bleeds tuned separately. We have 8 wide-band oxygen sensors on the dyno so we can graph what each cylinder is seeing for air-fuel all the way through the pull.