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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #1 ·
Bought the car a few months ago. All work was done by previous owner. 351W summit 600 carb. Motor rebuilt less than 2,000 miles ago, carb has less then that cuz he originally had Holley on it that he couldn’t get to run right. PO told when starting cold to push throttle all way down one time to set choke. Turn key. Worked perfect till weather turned cold. Last 2 times when it lights off it’s like the throttle is stuck wide open. Revs to the moon for a split second then comes back down. What should I look for that could be causing this?
 

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With engine off
Without seeing it my 1st thought to look down the carb while someone pushes the pedal.

Once I had a burr on the secondary linkage that would hang up once in a while.

Once I found it it was cured in 10 seconds with a small file
 

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Check for any interference in the current linkage. On my 390 with a Holley, I had to use a spacer to remove some slight contact which would cause it to hang.
 

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Sounds to me like the linkage is hanging up. Pressing the pedal to the floor squirts a blast of fuel into the carb and closes the choke, leaving the choke plate open approximately 1/8", but the throttle linkage should return to idle position.
You can check this without starting the car. Open the hood and take a photo of the linkage. Push the pedal down to close the choke, then look again at the linkage. If it's different than what's in your photo, your throttle linkage is hanging up.
 

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69 Fastback 351W .030 over, mild cam, C4
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146 Posts
Discussion Starter · #6 ·
Sounds to me like the linkage is hanging up. Pressing the pedal to the floor squirts a blast of fuel into the carb and closes the choke, leaving the choke plate open approximately 1/8", but the throttle linkage should return to idle position.
You can check this without starting the car. Open the hood and take a photo of the linkage. Push the pedal down to close the choke, then look again at the linkage. If it's different than what's in your photo, your throttle linkage is hanging up.
This is more along the lines of what it feels like to me . Hopefully I’ll get a chance to check it out this weekend.
 
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