Trying to see how fast some are going with vacuum secondaries and what spring, shooter combo.
I am trying Black spring next myself. Since the motor has a huge signal. Pulls 14" vacuum at 2000 cruise rpm. Signal in center carb is strong.

That is not the signal the opens the vacuum actuated
throttle plates. Its vaccum created just above the venturies (usually there somewhere) by the amount of air moving through the carburetor! I alawys used the lightyest spring!

I have three sets of six pak carbs, one mechanical set and two OEM Mopar vacume sets. One OEM set has been modified by C&J Engr. in Whittier ,CA(ask for John and tell him I cab sent you) that set runs real well, I have it set up with a bolt in the center carb. slide slot so it opens the secondary carbs as soon as I floor it, no bog, no hesitations The other set is a new set of replacement 1971 crabs that I have been playing with, they bog bad with the yellow springs I have rejetted the outboard carbs per Mopar latest race manual on jetting for drag racing,it runs good with that jetting once the bog is gone I dyno tested all three sets years ago when I put my pump gas 512 motor together, there was only 5 HP average differences between the the three sets the OEM set had not been rejetted then and it bogged stock bad on the dyno also Do you have the springs for the outboard vacume pods? If so try switching them around until you find the ones that make you happy BTW my car has ran as fast as 10:34 at 128.6 MPH with the good set of carbs on the 518 pump gas street motor in my 3450 lb Duster corked up I like it a lot I have no idea of what my motors(all three of them) vacume is at 2000 RPM cruising I should probally hook up a vacume gauge and find out

twin eddy afb's on a stock cross ram, times in sig.
That's a looooooooot of vac...

My thought is that since this motor is pretty tight and has a strong Ve it may need the heavy spring. I have tried the yellow ones NG.
Ran the brown ones and it is much better but still a slight bog. I have 50cc pum on center with 35 squirter. With tha air cleaner on and brown spring 11.8 & 118 mph.