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Butterfly Valve stuck open?
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Author:  SdSlant69 [ Fri Apr 19, 2013 7:56 pm ]
Post subject:  Butterfly Valve stuck open?
This is my first car classic car/project car. It's also my first car with a carb on it so this may seem like an obvious question...any quick info would be appreciated.

Got my car back from my mechanic and the butterfly valve is stuck in the open position. I had informed him that I will be rebuilding it asap (with help from a friend) so I'm not sure if he did a quick fix for a better idle or if this is how it's suppose to be. It wasn't like this before so I'm unsure. Can someone chime in?

Image

PS. Any suggestions on a good rebuild kit would be appreciated (I've already sent a request to Daytona Parts per SlantSixDan)!
Author:  wjajr [ Sat Apr 20, 2013 7:38 am ]
Post subject: 
That is the way the choke butterfly looks when the engine is warm. Its position is controlled via a bi metal spring that reacts to temperature; coiling tighter when cold, and uncoiling when hot.

Adjusting closing force of butterfly of a cold (overnight) engine start is made at the choke stove spring. Looking at the your photo at 12 o’clock there is a rod attached at butterfly axel shaft that extends out of frame in the direction of 9 o’clock to the choke stove pocket. Remove stove’s tin cover examine the bi metal spring, replace if broken, or make a tension adjustment so the butterfly closes when engine is cold, and fully opens when engine is hot. The butter fly should snap closed when throttle is cracked open when cold just enough to full seal, and once engine starts crack open via a vacuum pull-off (diaphragm at 3 o’clock with vacuum line attached) about 3/16â€￾ or so.

You need to check for binding linkage, broken bimetal spring, ruptured vacuum pull off, and high idle adjustment. Being from warm California someone may have adjusted bimetal spring to keep butterfly open at all times because they did not know how an automatic choke works
Author:  SdSlant69 [ Sun Apr 21, 2013 12:04 pm ]
Post subject: 
Dude, great explanation. Thanks for the help. I'll be taking a closer look today!
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