That dual 4bbl balance tube question again........

[427LX]

Okay when running the Tunnel Wedge intake manifold and a pair of vac. secondary Holley carbs is that balance connection really needed?  Now on the Chrysler
 426 Hemi with cross ram intake they ran fine without it with their 770 cfm vac. secondary carbs. The cross ram was like a pair of 4 cylinder engines running and same might be said with the
Tunnel Wedge looking like a pair of separate four runner intake manifolds. So how did both run well with and without.

[6667fan]

Are you running one to one carb linkage or factory progressive type? If progressive, the medium risers and low risers employed the balance hose. ( I don’t know about high risers).
Some aftermarket vac pods do not have nipples. I don’t run a connecting hose on my set up. ( no nipples, pods have opening rate adjustment screws).
I confirm both secondaries open. I run one to one linkage.

[Stangman]

Not sure if I belong in this convo but I have regular BT 2x4 and I’ve run progressive and 1to1 and either one  I run the hose. I believe it can be used without If just sort of makes sure they are coming on at the same time as the other. Just a little syncing together. I think on the track it mean less to have the hose because of the fact that we are essentially flooring it but around town I think it is a good idea.

[427LX]

Are you running one to one carb linkage or factory progressive type? If progressive, the medium risers and low risers employed the balance hose. ( I don’t know about high risers).
Some aftermarket vac pods do not have nipples. I don’t run a connecting hose on my set up. ( no nipples, pods have opening rate adjustment screws).
I confirm both secondaries open. I run one to one linkage.

I run 1 to 1 linkage. Took it out this evening and had a contact switch mounted at each carb secondary link. Hit it in a 2nd gear roll and both indicator lights lit up at same time. They were set to make contact at about half open. Loved it and it pulled hard lighting up the drag radials!

[6667fan]

That is a high tech way to confirm operation, very nice. I just old school a paper clip on each plunger rod. Push clip up against pod bottom. After a rip the clips are down at the bottom of rod (if secondaries opened fully).
 

[cleandan]

Sometimes the inverse of the question helps to clear things up a bit.
The current question, "Is the secondary diaphragm balance tube needed when running dual quad carbs"?

The inverse question, why should I remove the diaphragm balance tube? followed by the question, what will I gain by removing the balance tube?

[My427stang]

Here is my take, call it an educated guess.

Each vacuum secondary is opened by airflow across a hooded orifice or tube in the primaries.  In progressive linkage, your carburetor's primaries are opening at different rates on each carb, but not having them exactly the same for the primaries is OK as it is controlled like a mechanical secondary, controllable by your foot. 

I'd be concerned that in a non-balanced progressive setup, you could have airflow change in carb #2 as the secondaries opened significantly in carb #1 and delay or even oscillate the second carb. I would expect better drivability if the secondaries came in balanced between the two by the tube in that case. 

Can't say I have tried running without them though

In a 1:1 setup, the tube certainly won't hurt, but the primaries should be opening at a much more similar rate, so same airflow change pulling on the diaphragm, assuming you aren't using linkage that uses the different pivot points of a factory design, so the difference should be much less.  That would apply to yours, and also to Edel cross rams and Mopar cross rams.