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  #16 (permalink)  
Old 03-24-2013, 10:47 AM
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When my 440 had the .509 it made like 10 " of vacuum. I don't think it could have pulled the vacuum secondary open. The 750dp dumped it down the throat..

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  #17 (permalink)  
Old 03-25-2013, 02:16 PM
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Agreed, Venturi vacuum is generated with air velocity in a carb.
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Old 03-26-2013, 07:23 AM
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The vacuum secondary's open progressively based on the vacuum signal produced by the engine, regardless of throttle position.

Tuning the secondary pod you would start with a light spring, and go heavier until the stumble from opening to quickly went away. I dont think you could make it open faster, only keep it from opening too fast. Watching the vacuum secondary pull open on the dyno is quick, but not like a mechanical.

Last edited by spinn; 03-26-2013 at 07:37 AM.
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Old 03-26-2013, 08:20 AM
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Wrong my friend
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Old 03-26-2013, 09:45 AM
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This how it works
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File Type: bmp Vacuum secondary.bmp (1.46 MB, 35 views)
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Old 03-26-2013, 11:37 AM
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You are wrong. The pistons moving on the thing called a rotating assembly causes negative pressure. That is in every text book.

A venturi has no vacuum on its own.

I don't know if you are talking about an engine. You seem to be continuing to fixate on the venturi.

The piston pulls the air threw the venturi . The amount of pull by the piston is affected by the ivo/ivc.

Please diescet post 25. What are you saying is incorrect.
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Old 03-26-2013, 12:10 PM
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The comment on not being able to open , was a descriptor/illustrator for the idle quality. I do not want you to think the engine was actually not able to pull the secondary open to a tunable degree.

The comment on dumping , the fuel is still being induced in a metered fashion. Not actually dumping.

Now, please explain what you think is in error.
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  #23 (permalink)  
Old 03-26-2013, 12:20 PM
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Quote:
Originally Posted by lg1969 View Post
Agreed, Venturi vacuum is generated with air velocity in a carb.
What? That is pretty weak.

A venturi pulls a fluid with air velocity...yes

The air velocity is created by the piston downforce...yes.

The air door is controlled by vacuum.. yes

Last edited by spinn; 03-26-2013 at 12:25 PM.
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Old 03-26-2013, 12:24 PM
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Look in the Holley Book. It shows the same picture.
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Old 03-26-2013, 12:35 PM
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Okay we can do book quotes.

If you are in disagreement with what I typed please indicate the passage.
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Old 03-26-2013, 12:43 PM
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Quote:
Originally Posted by lg1969 View Post
Wrong my friend
Are you,LG, going to identify what was incorrect?
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  #27 (permalink)  
Old 03-26-2013, 12:51 PM
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What do mean? I read the book about Holley Carbs.
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  #28 (permalink)  
Old 03-26-2013, 12:53 PM
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Awesome. I like books too, and girls, and cars, and music. See we have things in common I bet.

The diagram is from holley, I do not have a problem with it.
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  #29 (permalink)  
Old 03-26-2013, 04:01 PM
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Here is some more info on page 6
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File Type: pdf Carburetor Tech Info.pdf (131.8 KB, 29 views)
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  #30 (permalink)  
Old 03-26-2013, 04:12 PM
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Do you have a question?

Have you seen the secondary function at load. The secondary opens similar to an actuator. A mechanical secondary linkage is fashioned progressive or not, wide open is wide open with 4 barrels.

On my old 440 even at wot it did not open all the way. It took some distance to pull the secondary open to its maximum. Even then it was not able to open all the way. Due to a stumble I had to spring it so it never opened all the way to get max cfm. I went double pumper. Both carb types tune and worked well. The dp was more correct for the application. There were many changes made with the carb swap, but I believe that it did improve the performance at the track.

Last edited by spinn; 03-26-2013 at 04:36 PM.
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