Carter Thermoquads ~ 'More General Information'

Bewy, on the subject of the large jets/air bleed sizing, the idle air bleeds and primary main metering bleeds on these 6090 and 9103 top lids are out of sight. the angled rearward and up idle air bleed, that goes down into the venturi area as a diminishing air bleed, will accept approximately an .050" drill bit. .048 is loose, .052 is a no go. there's yet ANOTHER angled down idle air bleed, racing DOWNWARD and rearward, in the bottom of cavity, where the main metering rods go through on the top. that one can't be measured, no room to do so. if the lid is removed from the carb, and carb cleaner sprayed into the idle passage in front bottom of carb lid, you can see those 2 idle air bleeds are tied together, both of them spray fluid. these TQ's have a mongo amount of idle air bleed emulsion. that's why the jets are so huge, in comparison to say a Holley, or Qjet.

then there's the primary metering air bleeds, facing straight up on the lid, just forward of the screw hole, that holds the little cover plates over the air bleed/metering rod holes area on each side. remove that plate, check out the size of those bleeds. they go directly down into the main well that feeds the primary nozzles/booster. those primary metering air bleeds are .077' on the 9103, and .087" on the 6090. massive.

there's yet another air bleed in the top nose of each primary nozzle. this is why they needed anywhere from a 92 to 104 main jet. there's a ton of air being used for emulsion and atomization on these carbs. it's really over the top.

again, the later 9103 carb has a smaller primary main metering bleed by about .010"
so it would be richer.
I had thought it was identical but it's not. I do not have a complete drill index in .001" increments.