Originally Posted by bumpstart

you can mod the TB so the delay for the secondaries holds out longer
with the simple mech link ones, you tighten the dash pot on the delay

with early ones with the thermo switch and pneumatic valve to hold off secondaries while warming up
you can re-route the pneumatic signal to come from the primary runner,, engine side
vacuum on this side will hold secondary delay throttles shut
they will open to same throttle setting as the primary when the primary porting becomes restrictive an 0 vacuum or load begins to build in the primary inlet

you may need to add a little pill and make a little pinhole in the vacuum line to the valve to prevent the engine continuing to accelerate by itself in high gears when you lift throttle

( as it can create a surge of pressure into the partly open primary throttle and give an almost cruise control effect ,, it will break the signal if you also clutch in and remove load from the engine )

to do this method you must have the right TB,, and i am unsure if this same early arrangement is avail on the NA TB