8 year old Holly Street Avenger 600 series. I have not ran the car much "out of the country and has been on blocks. Once running it was running, gas spilling out the top. I ordered a Holly rebuild kit and tore it apart....soaking all parts in carb cleaner. I took pic's and 99 percent sure it is put back together correctly. It is a vacume secondary carb....so I was not 100 percent sure it was not opening at WOT. I did put a paperclip in the vertical linkage controling the vacume lever....ran the car at WOT....the paper clip does not move...which tells me, diffinately the secondarys are not opening. Note: within the Holly rebuild kit.... tere was no new secondary diaphram? I did pull the diaphram out and looked at it with a light behind it....there seems to be no holes or cracks. I did replace the gasket between the secondary and the carb body! Any ideas? Thanks heaps!!

Note: When I manually open primarys.... I can manually open secondarys. i.e. there seems to be no linkage issue.

 

https://documents.holley.com/199r10219-3.pdf

download and go through Holleys instructions for setup.
If that doesnt help you can go to a lighter spring in the vacuum pod to make it open easier. At the bottom of page 10 there is good info on the secondary system and tuning

 

Can you test the diaphragm with a minivac?

 

I would think so..........

 

You may have to exceed 4000/4500 rpm to get the secondaries to open.
With your LT-1 that should be no problem

The paperclip test works.
And you must be driving the car, not still. 2nd gear works better than 1st.

If you can get a mityvac pump fitting to seal on the vac pod port, you can test it. You'll need a big flat rubber adapter. The kind that came with my vac gauge.
Or push the diaphragm rod up, pod off, seal the port with your finger, and let go of the rod. It should hold up as long as your finger is there.

Sometimes the diaphragms go on crooked and do not seal.
Install it in the pod, and compress spring with fingers by pushing rod up, to relax the diaphragm, then tighten the screws.

To tune the vac pod start with too light of a spring and you should feel a bog.
Keep going stiffer, in steps, until the bog is gone.

 

If your secondary vacuum diaphragm has the stock, out-of-the-box spring installed, your secondaries will not open at any usable rpm. You have to "tune" your secondary opening using the Holley secondary spring kit (part number 20-13). In most cases, the "purple" or the "yellow" spring will allow the secondaries to open properly. These are the two springs used by Holley on the GM-installed factory Holley carbs.


Lars

 

I did downloaded your link...come to find out...I have it Thanks! I followed that paper...but still not opening. ;(

I used to have that Minivac back in 2006....looks like I need a new one!


Not sure above...where to seal off with my finger? ;( Yesterday, I found a yellow spring....installed it with paper clip. I did not feel secondarys open and and to confirm...paperclip did not move!!

I pulled the original "silver" spring out yesterday and replaced it with the yellow....same results & with paperclip. Before I tested and installed the yellow spring...I leaned over try/did seal the opening with my mouth "after I removed the quick cap and spring" and could suck the diapram up....it seemed to have no leak?? Today, I will pull the secondary housing....to see if "it must be" the gasket to the body of the carb...must be leaking?

Anyother suggestions would be mucho appreciated! MW

 

YOu are not going to feel the secondaries open like you would on a double pumper mechanical secondary. If you arent going lean its probably opening. can you take off your hood and go for a ride and use something like the paperclip and have a passenger watch it or use a gopro or some sort of video recorder to record what is going on

 

As I indicated above....I used the paperclip....the paperclip is not moving! So, secondaries are not opening. I'm feeling a nice even pull "RPM gage is not workig" but would estimate RPM to be at least 5+K .

 

can you post a picture of how you are setting up your paperclip

 

When you remove the diaphragm housing assembly, put a vacuum hose on the hole for the vacuum port on the housing - there should be a thin, flat round gasket on it. Just jam a vacuum hose against the area around the hole and suck on it - the diapragm should easily "suck up". Next, use the "red straw" on your WD40 can and stick it into the vacuum port hole in the body of the carb that mates with the vacuum passage in the diaphragm housing. Give it a couple of squirts. You should see WD40 dribbling out of the vacuum hole in the passenger side rear segment of the primary venturi. If there is no dribble, the hole/passage is plugged. If there is WD dripping out the hole, and if you can suck on the vacuum hose to retract the diaphragm in the housing, you are getting vacuum to the diaphragm (assuming the gasket is installed), and nothing can prevent it from operating. You might want to disconnect the diaphragm rod from the secondary throttle shaft lever and run your paper clip test without the rod attached to the throttle - see if it moves.

 

I don't like the idea of tach not working.
You may be pulling the lever too soon, out of caution, with no tach.

You are going to have to rev it in 2nd gear to get it to open.
Suggest you figure out gearing vs rpm and use the speedo as you tach.
2nd gear 5000 rpm = x mph , 6000 = y, etc.

It's an LT-1. It wants to rev, let it.
to 6300 anyway.

Gear and trans?
If 3.70 gears and 2.20 M21 trans, then:
4000=52, 5000 = 67 and 6000 = 80

be very sure on the gears if you do it this way

My '70 LT-1 did not "flatten off" 'til 6700.

 

Make sure linkage opens from pedal for full open throttle. No floor mat under pedal.

 

I seem to remember, maybe it was in one of Lars' papers, that if you can feel Holley secondaries come in you don't have it set up properly. Found that to be the case in my '65 4150.
My wideband says WFO is spot on so it's doing what it's suppose to. WB's are the only way to properly t00n. My springs were too tight.

Even got my quadrajets to do same.

 

^^^THIS^^^ Very common !
Also, sometimes bottom of pedal is bent and restricting travel to WO. I've owned two C3 and both had suffered this.

 

Once I had the diaphram housing away from the carb body....I could immidiately see what the problem was. For some reason....the mating gasket "diaphram body/ carb port passage" had somewhat distorted and I think was blocking vacume from the secondary diaphram....;( I did use a vacume hose and held it agains the diaphram body port in which I applied vacume "mouth" in which the diaphram linkage moved freely. Thanks Lar's! I also took a small wire and tried to insert it into the carb body port....thru the gasket that was distorted....no go! Bingo!! It got late so was not able to test! Tomorrow should be a fun ride!! Thanks everyone for you're help!! Hopefully tomorrow, I'll be able to report a thumbs up with a smile & grin!! Cheers!!

 

Note that you can't push a wire all the way through the vacuum port hole in the carb body and out through the hole in the venturi: You can push it in about 1/4", but the passage then makes a 90-degree turn to intersect the venturi: You can see the "plugged" drill hole to the rear of the vacuum hole where they drilled the 90-degree intersecting passage in the carb body. But do spray some WD through that vacuum passage port and verify that it dribbles out from the hole in the primary venturi as noted - that will assure you that the passage is open.

The other note above by Interpon is valid: Have someone sit in the car and push the gas pedal to the floor. Verify that the throttle lever on the carb actually goes all the way to wide open throttle - the primary throttle lever linkage should hit against the WOT hard stop, and the primary throttle blades should be fully vertical. Very common problem. On most Holleys, you have to install the throttle cable in the lower cable attach hole in the lever in order for WOT to be achieved. Check and verify this: your secondaries aren't going to open if you are only getting 3/4 throttle opening (common on most Vettes). In my papers I refer to removing the floor mat as the "25-horsepower floormat removal trick."

 

Lar's/members....Test resulted in..., grinnig from ear to ear!! Said that, "Lar's" I did not use the WD40 to see if the passage was open....I knew it was due to soaking the carb body and all parts in a gallon of carb cleaner for over 24 hours when I had the carb complety disasembled. Matter of fact...I had to look all over in my neck of the woods to find a gallon of cleaner vers the spray cans.

btw: When go pedal was mashed to the metal/carpet...primary blades were vertical! Note: When the Admiral was doing mashing, I have no idea why she was also grinning from ear to ear!! LOL OMG...me thunks she wants to stay in the left seat!! OK Baby...but, no mashing, yea right!! I think she has her eye on Route 66!

Lastly...I do have a couple other issues "complety unrelated" and will post up soon. Thanks eveyone!!

 

Don -
Good work identifying the problem, tracking it down, and getting it resolved! I often receive carbs that have had "work" done to them that disables the secondary operation (both Holleys and Q-Jets), and the owners have operated the carbs/cars with inoperable secondaries for years without ever realizing it. Hope you have some fun with the car now!

Lars

 

Here is how I tested the secondary's. Used a video camera.