Six Pack secondaries have no vacuum

[oz]

Hi, I just picked up a '70 RR with a 440/6 barrel and noticed that the outboard carbs were not working. I replaced the torn diaphragms and corrected all the vacuum plumbing (outboards were connected to manifold vac, advance was connected to outboard vac feed. I checked the movement of the outboard butterflies and they move when I apply vacuum, although when I connect to the middle carb secondary vacuum they don't work. The reading on this port at any rev. is 0hg, although when I cover the middle carb intake with my hand I notice a very small vacuum (2-4hg), I've also ran I wire through this port to check for any blockages (there are none). I've since connected the outboards mechanically as a temporary fix, but I thought I would ask the experts what might be causing loss of vacuum on the secondary feed. Mopar newbie

[oz]

...also would like to add, my understanding of the port connections are as follows: center carb metering block port goes to vacuum advance, center carb port (points down) goes to secondaries.

[Troy]

Does this help?

Troy

[PRH]

Attach a vacuum gauge to the port on the center carb that goes to the outboards, and put the gauge where you can see it while driving(tape it to the windshield, etc), and then go out and see what kind of vacuum signal you get at wot.

After you know how much vacuum signal you have to work with, using a hand held vacuum pump(mighty vac), you can test the vacuum pods to see if that amount of vacuum will activate the pods.

I haven't tried this myself, so my thinking may be flawed here...... But that's what I'd try.

[Troy]

I'm not sure I ever tested this myself but you won't get vacuum unless it's under load. This is the opposite of distributor vacuum which is highest at idle then falls off. I'm not sure how you'd test it sitting still. How do you have it hooked up mechanically?

Troy

[oz]

I do know that I can engage the secondaries with minimal vacuum (suck test), I also know that the secondaries are definitely not engaging while driving. When I setup the linkage to mechanical this thing pulls like a freight train when I hit it.

[oz]

Does this help?

Troy

It looks like you have the vacuum advance blocked off and slightly below I see the secondary vacuum feed, I have the breather and manifold ports blocked off. thanks

[PRH]

It sounds like you've verified the pods will activate with vacuum, so the only answer is they aren't getting any at wot.

Have you blown air through the vacuum port on the center carb to make sure it's not plugged?

It should connect to a small hole in the venturi.

If its clear, I would still try the test with the gauge hooked up to that port and make sure it has vacuum at wot.

You're not really going to be able to do any worthwhile test of that without the motor under load, at rpm(driving the car, chassis dyno, etc), And at full throttle.

[John_Kunkel]

I'm not sure I ever tested this myself but you won't get vacuum unless it's under load.

Yep, you won't get the outboards to open when testing in the driveway. (well, maybe just before the rods come popping out of the block)

https://www.youtube.com/watch?v=tLx5vbCl4LU

[70sixpkrt]

http://st.hotrod.com/uploads/sites/21/2013/12/440-six-pack-carbs.jpg

[Troy]

Does this help?

Troy

It looks like you have the vacuum advance blocked off and slightly below I see the secondary vacuum feed, I have the breather and manifold ports blocked off. thanks

Actually, my vacuum advance is flipped. I had FBO build me a distributor to work that way with the Six Pack. However, my secondary connections should be correct.

I'm not sure I ever tested this myself but you won't get vacuum unless it's under load.

Yep, you won't get the outboards to open when testing in the driveway. (well, maybe just before the rods come popping out of the block)

https://www.youtube.com/watch?v=tLx5vbCl4LU

   

Troy