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Old 06-29-2009, 08:11 AM
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Secondaries Issue

Hello everyone. I'm having problems opening my holley's secondaries.

350 engine, automatic.

Brand new, out of box, Holley street avenger 670. Vacuum advance is set on ported not manifold vacuum. runs and drives great, a lot of power but, secondaries are not opening AT ALL. I know this from the 'paperclip test' and I just dont feel and hear the power when I should. Yes, I am testing it while driving not free revving the engine.

I'm puzzled because I had a different holley on it before and those secondaries would not open at all either. I tried the putting the lightest spring in there, still nothing. When the pedal is all the way down it IS getting full throttle. Could it not be getting enough vacuum?

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Old 06-29-2009, 08:31 AM
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If you are using the lightest spring and still no 2'ndary opening, I would check to see that the check ball (Part #68) is not sticking. I lightly stake an old ball into the seat that it rests on to assure a good seal, then remove that ball and re install the check ball that is to be used.

Also, be sure that the (p o s) cork seal (part #60) is still present between the 2'ndary diaphragm housing and the carb body. I use a small amount of hylomar on both sides of this seal.

You have to check for proper operation of the housing/diaphragm before installing it onto the carb. This is done by mouth, drawing into the vacuum port to see that the diaphragm lifts the rod and that the vacuum is held- no leakage is allowable.

There can be no blockage of the vacuum passage that operated the 2'ndaries, either. Use carb spray down the orifice to see that it's not blocked.

If you've done all that and still no 2'ndary- your engine is such a wheezer that it doesn't need the 2'ndary.
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Old 06-29-2009, 08:48 AM
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thanks for the reply. This carb does not have the check ball, it has the fixed brass piece instead. Since this is a brand new carb I haven't taken much of it apart but I would sure hope it has all the necessary gaskets and proper tests. BUT, the other holley I had (which the secondaries were not opening either) I did test vacuum and it held it great, I also cleared out any and all passages still no luck.

I've just not been having luck with these holleys
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Old 06-29-2009, 08:58 AM
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Quote:
Originally Posted by nealkal
I've just not been having luck with these holleys
Luck aside, the engine has to "need" the extra flow. In order to need it, the engine has to be wound out pretty damn far- if it's a stocker- to get them to open.

The average AT tranny, if left in "D", won't usually let an engine wind high enough to get the 2'ndaries to open. You may need to manually hold and shift the tranny, using a tach to keep track of the revs.
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Old 06-29-2009, 09:03 AM
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Good point, thanks. I have a 350 stock engine (except for aftermarket Edelbrock intake). 350 automatic trans and a B&M shift kit. 4:56 gear ratio in the rear end (or so I was told by the guy I bought it from) What is the rev limit or red line in this setup?

19.5 in of vacuum from manifold at idle.
11 degrees btdc
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Old 06-29-2009, 09:19 AM
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Quote:
Originally Posted by nealkal
I have a 350 stock engine (except for aftermarket Edelbrock intake). 350 automatic trans and a B&M shift kit. 4:56 gear ratio in the rear end (or so I was told by the guy I bought it from) What is the rev limit or red line in this setup?

19.5 in of vacuum from manifold at idle.
11 degrees btdc
The engine is safe, mechanically-speaking, to at least 6500 RPM. Max power is prolly around 4500 RPM.

If you have 4.56 gears, the engine would "red line" VERY quickly, even if stock, and would be "wound out" at 65 MPH on the highway- to the point that you'd be wishing for the trip to be over with!

First gear would be over with in a blink before second gear would be there, then third shortly thereafter. Quick 1-2-3.

Because your engine really sees no real amount of low vacuum conditions, this is also working against you having the 2'ndaries open.
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Old 06-29-2009, 09:43 AM
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Few questions: Why would my engine not create enough low vacuum? Wouldn't it need high vacuum through the carb to open the secondaries? How would having the secondaries open work against me? How can this be fixed?

Last edited by nealkal; 06-29-2009 at 09:54 AM.
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Old 06-29-2009, 10:32 AM
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The secondaries pick up a vacuum signal from the venturi of the primary side that starts them opening. At some point after this initial activation by the primary venturi vacuum signal, the secondary side adds to this, opening them further.

Possibly, your engine simply isn't under enough load to need the secondaries to open, or there's other mechanical problems w/the carb.

The diaphragm has to be properly orientated, for example, or the vacuum port is covered up by it.

There are at least 3 different diaphragms- it has to be the correct one for the app.

How it can work against you is if the engine doesn't need the extra airflow, it'll bog if it gets it.
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Old 06-29-2009, 10:40 AM
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A decent site to visit (besides Holley itself) is http://www.bob2000.com/carb.htm
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Old 06-29-2009, 10:57 AM
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Great info, Thank you. I bought a secondary diaphragm to replace the existing one to rule that out and I noticed it does look different. For example, the one I just bought has a circular bubble in it such as this

http://www.bob2000.com/vacassy02.jpg

While the existing one looks flat.

Would this make that much of a difference?
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Old 06-29-2009, 11:59 AM
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Quote:
Originally Posted by nealkal
Great info, Thank you. I bought a secondary diaphragm to replace the existing one to rule that out and I noticed it does look different. For example, the one I just bought has a circular bubble in it such as this

http://www.bob2000.com/vacassy02.jpg

While the existing one looks flat.

Would this make that much of a difference?
It could- w/o the "bubble" it would be difficult for the vacuum to pull the diaphragm, like a speaker w/o the foam roll around the edge.
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Old 06-29-2009, 12:14 PM
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Ok, I will switch them out and let you know what happens. Thanks for all your help!
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Old 06-30-2009, 07:39 AM
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Ok, I worked on this more last night. Checked all seals, gaskets, and pasages and everything is in great condition (brand new carb). I took the secondary diaphragm out and it was actually fine. I tried the lightest springs and it didnt open at all. Just out of curiosity I took out the spring completely so there was no secondary spring in the housing and it opened about a quarter inch (looking at paper clip).

I also thought that maybe the air cleaner wasnt allowing enough air flow so I ran without it and still no opening. Gas pedal opens the throttle cable completely.

I also tried shifting manually and reving up to about 5500 (normally shifts at 4000 to 4500), still nothing.

I'm starting to think my engine does not pull enough air to open the secondaries. How could this be? and how could this be fixed?

73 el camino (too light of a vehicle to create enough load maybe?)
350 stock engine (execpt edelbrock intake)
headers
3 inch down to 2.5 inch exhaust
350 auto tranny
B&M shift kit
4:56 rear end (or so I was told by guy I bought it from)
11 btdc initial
19.5 inch of vacuum at idle from manifold


Could any of these specs be related to the engine not pulling enough air through the carb to open the secondaries?
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Old 06-30-2009, 08:12 AM
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Actually, a restrictive air filter will light off the 2'ndaries quicker than none or a free-flowing filter.

The gears and the stock condition of the engine could be part of it, but I would still expect it to open the 2
'ndaries up. But in thinking back, I've never had a Holley on a completely stock-spec engine.

With no spring, I can't see how it couldn't pull them open.

Try taking out the check ball out of the diaphragm housing and use the lightest spring and see if it is what's preventing it from opening. I'm thinking it will help.
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Old 06-30-2009, 08:26 AM
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With this street avenger it doesnt have a check ball it has a brass piece instead. Can that be taken out?
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