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Discussion Starter #1
Can any one tell me if my engine "should " die when I back the idle screw all the way out and close the throttle plate all the way...........because it does not.

I have been chasing what seems to be a vacuum leak and was told that I had a vacuum leak if the engine did not die when the throttle plate was completely closed. This is on a holley 670 street avenger.

We have checked all the usual places for the leak (sprayed carb cleaner mist around all the manifold runners, plugged off all the vacuum ports, etc).............jerry
 

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It does sound as if you have a vacuum leak, But taken into consideration, how much are the secondary`s open? they can be open enough to keep the engine running at idle. however it could have a leak on the bottom side of the intake gaskets, which will also suck in oil and usually cause a part throttle stumble, in one case I used a Edelbrock performer that I couldn`t get to seal up no matter how much blue glue I used on it, so I took it to have the straightness checked, it was warped so my machinist says "I can mill it and save it" he took .020 off it and it was still warped, so it hit the trash. sometimes carb cleaner won`t detect a leak, try a propane torch, turn it on without it lit and go around the base of the carb and around the intake.
 

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"May the Schwartz be with you"
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Use the unlit propane torch trick, go around all the seals (carb, manifold, vacuum lines, etc...). I do not like to use carb cleaner as I have seen it catch fire on hot headers.

If you have a leak you will know.
 

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Technical Support Barry Grant
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Secondary butterfly adjustment

To adjust the secondary butterflies you'll need to remove the carburetor from the vehicle, and see how much of the transfer slot is exposed below the butterflies. If it is too much you'll need to close them on your Holley there should be a small screw going through the bottom of the baseplate to control how for the secondary butterflies are open.
 

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Discussion Starter #8
BG......when you talk about the secondary slot being exposed to much .......how much is to much?.....and where should it be set or is it an experimental option.....stinky
 

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Technical Support Barry Grant
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The amount will vary depend upon how the carburetor is setup. Normally on a street car that idles below 1000 RPM we set the secondary butterflies right to the bottom of the transfer slot. This would mean you would not see any of the slot (below the butterflies) at idle, but you'll start to see it with any movement of the butterflies.
 

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Discussion Starter #10
Tech @ BG said:
The amount will vary depend upon how the carburetor is setup. Normally on a street car that idles below 1000 RPM we set the secondary butterflies right to the bottom of the transfer slot. This would mean you would see any of the slot (below the butterflies) at idle, but you'll start to see it with any movement of the butterflies.
BG......Did you mean to type "not" see any of the slot" in your responce....thanks..jerry
 

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Technical Support Barry Grant
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Yup..
 
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