It's a 870 street avenger. I have went all the way to the weakest spring and they still don't seem to be opening. I tied the secondaries closed.... no perceptible difference in the power... Any suggestions?
It's a 472 alum headed hemi with the M/P dual plane manifold- Comp 292 hemi cam.
Thanks
Glenn

You know you have to have the motor under load for the secondaries to open, right? You just can't wing the throttle in the garage and see them open.

Brawls- Notice the statement "no perceptible difference in power with the secondaries tied closed"? Yes I am road testing it at full throttle and Yes, I am aware, they will not open while winging the throttle in your garage
Glenn

Hey Glenn, did you check to make sure the secondary plates are not binding? Open the primaries all the way and then check to make sure the secondaries open freely and are not stuck. The vacumn diaphragm has a cork gasket between it and the carb, it's in the port between the two close together mounting screws that hold the diaphragm chamber to the carb. If you have an electric choke you need to remove it to get the vacumn chamber off.

What 3twos said.

You can use compressed air to open the secondaries with the carb on the bench, if it'll make your troubleshooting go any easier. You'll see a tiny tube in the pass side primary venturi that passes to the vac sec pod. Just blast some air past that tube and the secondaries will pop open if eveything is working properly.

Holley recommends to put a paperclip on the shaft
of the secondary rod and go run it, the paperclip
will slide down if they are opening up under
load out on the road.

Another thought is maybe that pasage isnt fully drilled? On that engine it's a small carb, and it should almost fall open...

1. I have a set of vac sec tuning springs. Holley say to keep going lighter till there's a bog and go back one. I went from red all the way through yellow, short yellow, to the white? one. Still no bog
2. I tried the paper clip test... twice. The result was inconclusive. The tension on the paper clip was tight first and vacuum pot didnt move. I loosened up the paper clip and it moved too easy.
3. After scrapping the paper clip idea, I tied the vac secondaries closed and tried the car at full throttle. I couldn't see any difference in the power

I am leaning towards the previously mentioned plugged port. Like you said Al- Quality control sucks
Glenn

Al- How's that AAR runnin'

Al:
The secondary butterflys are free and not sticking/ binding when closed. I will pull the secondary diaphram assy off and have a look
Glenn

Place the carb on tight enough that you can bearly move it then move the carb toward the rear all the way and snug down. Do not overtighten. I also fixed a street venger the other day that has a vac bladder that was not placed in right and as a result they wondered why the car was a dog. Take off the vac pot and check to see if it is not leaking around the edges

Thanks.... Shoulda bought a double pumper!!

Placing the diagram in the vacuum pot takes extra care. Any leak and it's not going to open.

I have also heard of the small fiber O ring betweent he vacuum dashpot and the main throttle body not being placed properly on them. Still one of my top choices for carbs. It's not the design, it's the execution, and Holley is still overall one of the best "out of the box" places.

Al/Jim:
When I pulled the secondary vacuum pot off, I shot a little brake clean into the vacuum port underneath and it shot out through a small protuding tube in the (pass side) secondary venturi. There's a flush hole in the (pass side) primary venturi but it don't seem to be connected to the vacuum secondary port... What do you think?
Glenn

Buy a big DP and just be done w/ it....

Hi Glenn,
first: my english is not the best...but my heart beats mopar

I have the same problem with the sec. My engine is a 383cui, with a weiand dual plane and first with a standard 600 Holley. All the basics are o.k. But the sec. will not open. (I have 2 Micro-switchs on the sec. to see on 2 LED's on the dash what's going on) If I open the primarys and blast a little air thruogh it the sec. opening very easy. (with the white spring) The same play with a 625 Road Demon and a 650 Speed Demon VE. If I drive a Kickdown from 3rd to first the sec. open 30% but not if I drive all gears manual until 5500rpm with throttle full open. What the hell is the problem ?? Have you find a solution until now ? Greetings from Germany Mario

My 770 avenger acted the same way. I pulled it off and dropped on a 4150 750cfm and would never go back to VS. This is on a 408 in my Dakota. I wanted vacuum secondary's to help lessen tire spin when I drive around town. I just gave up on that idea all together. I am not impressed with the avenger I had on the engine.

if the hole that goes from the vac. pod to the pri. venturi is blocked or not drilled all the way thru the sec. will never open.If you tune a 3310 carb right it will be only a few hundredths difference in the sixty foot compared to a double pumper.There is some things you can do to make the sec. open so fast you will need to install a 50 cc pump on the carb to overcome the bog.