Had fun with my good buddy Dr240z refining the tuning of his triple webers.
The last time we set them we used a fuel level of 25mm below the cover-body margin (as per Keith Frank's recommendation). It turns out this is way too high and caused the cruise to be too rich... something that could not be tuned out. Idle and WOT were easy to set however.
This time we set the fuel level to 29mm and used a new rig to do this as precise but much faster than the pipette method or the caliper method.
It turns out that a column of water 8' to 9' high "head" gives a pressure of 3.5 to 4 psi at the base (simulating that of the fuel pump on a Z.) so we strung a funnel and hose near the garage ceiling and ran this into a carb lid on the floor.
The carb lid sat on a clear plastic tub with water levels from the top scratched into it for reference. the top of the tub represented the top of the carb body.
By filling the system with water, it flowed through the needle valve at ~ 4psi. When the flow stopped, we measured the fuel level and bent the float tabs as required to get 29mm.
Once all 3 carb lids were the same, we continued tuning and finally dialed in the carbs to a powerful yet non-stinking/non-fume delight at idle, cruise, and WOT.
FYI: Gasoline would have been more accurate but water worked and was safer. FYI the S.G. of gas is ~0.70 so a float would sink lower in it.
29mm fuel level