Holley secondary's won't open - 460 Ford Forum
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post #1 of 30 (permalink) Old 04-26-2017, 11:06 PM Thread Starter
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Holley secondary's won't open

I have a 18 year old Holley 770 Street Avenger vacuum secondary. I have verified the secondary's won't open. I used the paper clip on the linkage and it didn't move. I bought a new diaphragm but when I pulled the housing off before splitting it open, I checked it with my vacuum pump/gauge and it works. So I replaced the little gasket between the housing. Blew some carb cleaner back thru the hole and verified the passages are open. I put it all back together and it still didn't work. I took it back off and tried blowing air thru the venturi above the small port. Stiil didn't work. I replaced the diaphragm anyway, still didn't work. I took the spring out and put a yellow spring in (lightest). Still didn't work. Took the spring out completely and it moved but didn't open. I have an old 750 on the shelf so I checked it. It worked. I swapped the housings between them and the 750 will work with both but the 770 will not work with either.
Any ideas what's wrong with the 770?

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post #2 of 30 (permalink) Old 04-27-2017, 07:43 AM
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Did you confirm that you can manually open the secondaries while the carb is bolted to manifold (no interference)?
Make sure the secondaries don't close so far as to jam themselves in the bore.

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post #3 of 30 (permalink) Old 04-27-2017, 10:17 AM Thread Starter
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Did you confirm that you can manually open the secondaries while the carb is bolted to manifold (no interference)?
Make sure the secondaries don't close so far as to jam themselves in the bore.
Thanks, yes, secondary's open on the intake manually. I checked and rechecked that as well as if the primary's open all the way with the throttle linkage. Also I have actually opened the secondary's a bit for idle speed (big cam overlap). Nothing binds or is jammed.
One reason I went to checking with the air nozzle was to eliminate a lot of variables. It seams to be a problem with the carb body I am thinking. They will try to open (using the air nozzle) with no spring at all. You can see them sort of flutter with the yellow spring but not open. It seams there is not enough low pressure drop (vacuum) coming from the venturi. The carb has been on the car a long time but has never been rebuilt. I did blow air and carb cleaner thru the hole while the vacuum diaphragm body was off. It looked clear, at least air and carb cleaner come out of the holes in the venturi, but the secondary's are defiantly not working right. I did the air nozzle test on the work bench. Side by side with the 750. The 750 works like a charm, the 770 does not.
As stated I swapped the diaphragm body between the two and both work on the 750, neither work on the 770. I thought maybe the parts weren't making a good seal or housing was bad or any number of things but I can swap parts directly to the 750 and it works. Parts that work on the 750 I can put on the 770 and it doesn't work.
Thanks

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post #4 of 30 (permalink) Old 04-27-2017, 11:11 AM
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I don't have any more advise - other than if the carb is 18 years old, you got your money out of it. Maybe someone else will have some advice for you.

Other wise, I suggest you use the 750 body and build up a working carb from that.

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post #5 of 30 (permalink) Old 04-27-2017, 01:52 PM
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IIRC, Something in the linkage keeps the secondary from opening if the primary is not fully open and the choke too. Did you find that part of the linkage?
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post #6 of 30 (permalink) Old 04-27-2017, 01:59 PM Thread Starter
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IIRC, Something in the linkage keeps the secondary from opening if the primary is not fully open and the choke too. Did you find that part of the linkage?
yes, you are correct. There is a part of the linkage connecting the primary's to the secondary's. Mostly I think to close them because once they are open the port in the secondary venturi will keep it open. But yeah, that isn't it. I did my bench test on both carbs with the primary wide open. Also verified when on the car at WOT the secondary's will open manually. Thanks though

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post #7 of 30 (permalink) Old 04-27-2017, 02:00 PM Thread Starter
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I don't have any more advise - other than if the carb is 18 years old, you got your money out of it. Maybe someone else will have some advice for you.

Other wise, I suggest you use the 750 body and build up a working carb from that.
you have a good point!

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post #8 of 30 (permalink) Old 04-27-2017, 04:12 PM Thread Starter
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here is a quick video
https://youtu.be/yJ1BkqH2H58

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post #9 of 30 (permalink) Old 04-27-2017, 07:33 PM
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Not to ask a stupid question....
but have you taken a handheld vacuum pump and seen if the secondary pod will in fact open?
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post #10 of 30 (permalink) Old 04-27-2017, 08:10 PM
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This may help:
Yellow Bullet Forums - View Single Post - Carb tuning help (first time tuning a carb)

www.supermotors.net/22468

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post #11 of 30 (permalink) Old 04-27-2017, 08:18 PM Thread Starter
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Not to ask a stupid question....
but have you taken a handheld vacuum pump and seen if the secondary pod will in fact open?
yes. the the vacuum diaphragms both work. They will work on the 750. I did check that before changing the diaphragm. In the video I posted you can watch it open.

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post #12 of 30 (permalink) Old 04-27-2017, 08:25 PM Thread Starter
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interesting I never heard of this. However, my 770 used to work so I don't think that not having that brass nipple/tube is the reason it doesn't work anymore. The 750 doesn't have one and it does work. But the whole thread is a great read and does get me thinking the port might be restricted on the primary side. Thanks for sharing that! I might drill out the lead plug just to inspect the hole. I have nothing really to lose at this point!

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Last edited by TARA-fied; 04-27-2017 at 09:22 PM.
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post #13 of 30 (permalink) Old 04-27-2017, 09:41 PM
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Tara-fied if you can get access to a carb dip tank you might try disassembling it and soaking the main body overnight and using the spray cleaner and air in the passage again any obstruction in that passage no matter how slight may cause your problem, eductor type devices don't respond well to any obstruction, also closely examine the venturi area of the bore for any nicks,burrs,or any other kind of damage that may disrupt airflow near the passage,small damage may be able to be smoothed out with emery cloth,larger damage may require more extensive repair that rapidly becomes a matter of diminishing returns.Also check the end of the passage next to where the diaphragm housing bolts on you will see where they drilled the passage and plugged it with a piece of lead or soft metal make sure that plug hasn't gotten loose and is leaking, a backfire can cause a holley to do all kinds of weird things simply because it ruptured a power valve diaphragm or loosened a plug.
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post #14 of 30 (permalink) Old 04-27-2017, 10:43 PM Thread Starter
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THANKS John!!! I inspected it tonight. The lead plug "looks" okay. The venturii looks fine and feels okay. I will disassemble and try soaking it. Any recommended product? I don't know any shops that still rebuild carbs but back in the day I used take carbs disassembled to a local parts store and they would soak it.

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post #15 of 30 (permalink) Old 04-28-2017, 06:48 AM
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Sorry, was offshore and so couldn't watch videos.

The brass nipple is essential.
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