Dual plane vacuum

[BOOT]

Do you read or compare vacuum on each plane in a real divided dual plane?

[cjperformance]

Do you read or compare vacuum on each plane in a real divided dual plane?

If its truly divided right up to and past the carb throttle plates and has no PCV connecting the 2 sides and no vac ports that intersect the 2 sides and no common connection from powervalve feed etc etc to balance the vac then yes you could/can.
If its not 100% divided then things like the pcv and powervalve feed or other various shared vac paths on many carbs will balance out 'small' differences.
Are you chasing a problem ?

[BOOT]

No problem I don't even have a setup like that atm. I was just reading some other junk and it kinda made me wonder about it.

[gnicholson]

its a common diagnostic practice to kill 4 cylinders on each side of the manifold and see if the rpm drop is approx the same for both sides. good test for idle circuit problems

[MadBill]

Since the carburetor would have at least one barrel per 'plane' opening in synch, the vacuum in each would be the same.

[Geoff2]

Just about every 4bbl has a slot/passage in the base that connects both sides of the carb for balance/vacuum equalisation purposes.

[BOOT]

and if it don't?

[MadBill]

Then each half of the engine inhales exclusively from one side of the carb. As a divider is notched wider/deeper, more capacity from the other bank is used, reducing the high RPM restriction but also reducing the pulse 'signal' to the carb and potentially hurting low speed torque. Cut the divider out entirely and you have a badly-designed single plane manifold, likely with distribution issues.

[BOOT]

Yah MadBill I totally agree, I'm just saving for vac. I know you said it'd be the same but other factors may effect it I'd think or even the slight plenum size difference. Well it at least may show something is wrong.