No vacuum to open outboards on a 6 pac

[r15303]

I am checking the vacuum to open the outboard carbs on my 440-6 and found there is none.  I rebuilt all 3 carbs with new parts and gaskets - made sure all passages were open - used Holly gaskets and made sure no holes were blocked.  This was happening before I rebuilt the carbs too.  I have great vacuum advance  - 25mm at about 3000 RPM.  Any ideas why this is happening?   

[MEK-Dangerfield]

Are you checking the vacuum to the outboards at idle? If so, they aren't supposed to open at idle, only under load.

[gkring]

The rubber vacuumn line is just a balance tube so they open even front and back. The signal comes from in the throat of the carb. Tiny hole barely visible as you look down the throat. obvious when you take the vacuumn pods off rebuilding the carb. Very rarely will you be able to get them to open without being under load even if you are winging the throttle. even if you plug the holes with your fingers and apply vacuumn to the rubber line the throttle linkage prevents them from opening. As long as your diaphragms aren't blown they are probably opening.

[Moparal]

Mine open when in neutral and winging it.  Did you check to make sure the throttle blades opened up by hand when you mounted the carbs before hooking up the linkage?   

[Chryco Psycho]

are the hoses connected properly ?? if you hook the dist & carb outlets backward the carbs will not open properly

[ShelbyDogg]

Some of those carbs were from the chevy tri power setup with the mechanical linkage and you have to open the passage by drilling the hole or knocking out the plug. I forget which.  All you have to do is suck on the hose going to the front or rear pods. You should be able to suck with your cheeks and hold the vacuum with your tongue. If the hole is not there, you will not get vacuum to the pod and it will not move. Trace the hose to the pod passage and you'll see what has to be done. Take off the pod and suck on the hose. Now suck on the pod and you'll see it move.

 I've only run into this once, so please post a pic of the clogged passage for others to see.

[r15303]

Thanks Shelbydogg.  Will check it out and if that is the problem, I'll post pics.  The vacuum pods do work by sucking on the hose.  The problem appears to be with the carbs.

[ShelbyDogg]

Put a paper clip on the shaft of the pod right below the pods, then go for a drive and give it a good heavy-load, WOT run. Pop the hood and look at the paper clips. You'll be able to see how much they open by how much the clip went down the shaft.  If they only open part way, that's when you get a couple of holley vacuum advance spring kits and put in some lighter colored springs. With the different colors, you can adjust when and how fast they open.

[Chryco Psycho]

if the diaphragms are torn or cracked or have any leak issues the secondaries will not open

[r15303]

Neat idea with the paper clips!  I wondered how I was going to check to see how far they opened - once I get them to work.  I do have a spring set from Holley so I'm covered there. 

[340_6pak]