Engine Run-On
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Tuned
Joined: Jul 2010
Posts: 432
Likes: 34
From: West Fort Worth, TX
I do not have a misunderstanding of the mixture screws and understand they r to adjust the a/f mixture. What I am trying to understand is the difference between the idle screws (pri &sec) and idle bypass screw which is down the hole for the air cleaner stud?
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Joined: Apr 2004
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Idle bypass leaves the throttle plates where they belong, and allows more or less air.
"The idle bypass valve allows for additional airflow through the carburetor, while maintaining the desired relationship between the throttle plate and the transfer slot. Applications using a larger cam may benefit most from this new feature. This valve replaces the need for holes in the throttle plates."
"The idle bypass valve allows for additional airflow through the carburetor, while maintaining the desired relationship between the throttle plate and the transfer slot. Applications using a larger cam may benefit most from this new feature. This valve replaces the need for holes in the throttle plates."
Thread Starter
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Tuned
Joined: Jul 2010
Posts: 432
Likes: 34
From: West Fort Worth, TX
Ok. So my original issue of engine run on could b attributed to my primary throttle plates being opened enough at ignition off after running to allow a vacuum along with rich fuel mixture and higher than recommended idle for my application. This was because I only adjusted the curb idle screw on the primaries after setting the timing. I will close that screw and try to adjust the idle bypass screw to get it running at correct idle. Then see where we r. Thx.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
The idle bypass adds air flow, the mixture screws add fuel.
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Tuned
Joined: Jul 2010
Posts: 432
Likes: 34
From: West Fort Worth, TX
I adjusted the idle screw back out and adjusted the idle bypass valve to bring the idle to 600rpm. I then fine tuned the a/f mixture to lean it out a bit. I drove the truck 25 miles and no run on. Thanks for all your help.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
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