Hate to be the bearer of bad news, but I doubt this combo will ever run properly. Too much carburetion & not enough cubes.
I would try this if it was mine:
- progressive linkage so that first 1/3 of throttle movement engine runs on the primaries of the rear carb; final 2/3 of throttle movement, all 8 barrels get to full opening at WOT.
- front carb: remove piston springs so that rods drop down. Find some wire [ a piece of stranded copper wire ] that is the size of the idle feed tube. Should be 0.031" to 0.036" range. Poke about 1/4" inside the IFR, bend the rest over & soft solder to the IFR tube [ to keep wire in place ]. Do both IFRs. [ Can be removed at any time ]. Screw mixture screws all the way in until seated. [ Idea is to ensure idling & low speed cruise is all done by rear carb ]. Close the pri t/blades until they are fully closed, but not binding in the bores.
- with front carb contributing less idle air, idle speed may be too low. So bypass air needed. Drill a small hole in the secondary [ not primary ] blades of the front carb. This is to distribute air more evenly.
