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Discussion Starter #1
How can I tell for sure if my vacuum secondaries are opening under acceleration?

It just doesn't seem like I get the extra power when I really step on it, but then again they could open really easy and just be open almost immediately...

Is there anyway to test this while the carb is in operation on the car?
 

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Holley trick - put a (lite) paper clip on the shaft coming out of the vacuum secondary housing. Make sure it is snug to the bottom of the housing. Take her for a run up to 2000-2500 rpm and then floor it. When you check the clip it should have moved down the shaft because the diaphram would have contracted under vacuum pulling the shaft up.
 

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The paper clip trick sounds neat, never thought of that one.I just popped the c-clip off the linkage where the vacuum diaghragm attaches and disconnected the diaghragm.Take it for a spin and you should notice a big decrease in performance when you punch it.If you don't they're probably not working.

<font size=-1>[ This Message was edited by: frdnut on 2/2/02 12:01pm ]</font>

<font size=-1>[ This Message was edited by: frdnut on 2/2/02 12:05pm ]</font>
 

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Discussion Starter #4
Wow, such simple ideas... that I couldn't for the life of me think of!!!!

I will test them out tomorrow. Hopefully they are not working... because once I get them going...well you know...

Thanks.
 

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Discussion Starter #5
I did the paper clip trick and there was movement of the plunger up from vacuum, but it didn't seem that much. I also tried taking the secondary shaft off, and I didn't notice much of a difference in performance. So I think they are not opening all the way.

--> Would a lighter pressure spring on the vacuum secondaries allow them to open further?

Also there is a linkage that comes from the main throttle lever on the carb and looks like it prevents the vacuum secondaries from opening until the main barrels open...

--> Would there be any harm in removing this linkage besides lower gas mileage?
 

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Don't remove the link between the primary and secondary shaft. It is on there to close the secondary when you let off the throttle. If it isn't there and the secondary stays open, it's just the same as a stuck throttle.
 

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You could have a bad vacuum scondary diaphram or missing the check ball. Get the replacement vacuum unit that has the removable top for changing the springs and the spring kit if not included. This allows you to change the srpings without removing the whole vacuum diaphram assembly (you might have this already and just need to install a sfter spring).
 

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Get the $10 secondary spring set. You can check the diaphram when you try the next weaker spring (I also recommend the quick change thingy). The advice I got on this site worked well - Go down one spring at a time. Take a little time getting the feel of the new spring, I found that a good stop and GO ride on and off the freeway helped. When the spring got too week she would noticably bog when floored, a real dog. When this happens back off to the previous stronger spring.

Another word of advice is check your power valve to make sure it isn't blown. Mine was and I got an inconsistent results and then had to go through the process again once I'd replaced the valve.

Still another word (I went through a lot of trial and error, emphasis on the error) that you may need to consider your main jets. Once I got the secondaries opening nicely I jetted down 2 sizes with no performance change but increased mileage (I was running a little right). I am basically at sea level so this probably helped.
 
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