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Discussion Starter #1
I've monitored several posts on the topic, but now I need to have the subject summarized for me. I'm trying to adjust the idle on my stock 351C-2V. My car idles very slow. I recently cleaned the carb and replaced the fuel filter. Afterward, I used a vacuum gauge to adjust the idle (it was the only tool available to me at the time). Using the vacuum gauge, I got the idle to max vacuum but this resulted in a still slow, albeit better, idle (especially at startup) and I wound up with my mixture screws at 3.5 turns (passenger side) and 3 turns (driver side). Many posts state that I really only want these screws equally set about 2.5 turns out.

So, I've adjusted the screws 2.5 turns out each. The idle is back to a slow idle requiring me to nurse it until it runs for a minute or two. What should I do next? Obtain access to a timing light?

  • Here are the most recent changes to my engine:
  • kitted and cleaned 2100 carb
  • new fuel filter
  • new Pertronix Flame Thrower coil
  • New Pertronix Ignitor electronic ignition
  • new rotor
  • new distributor cap
  • new 7mm plug wires
  • new Autolite 25 spark plugs (gapped at .040)
I don't have the vacuum gauge any longer, so I cannot tell you what the level of vacuum is. Nor can I tell you what my timing is set to now, since I haven't borrowed a timing light. I know this is a little light to go on, but I'm just looking for my next direction.

Thanks!
 

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You need to see where your timing is set at.
SOunds like your high idle screw is not set right on your choke.you adjust your idle mixture screws with the vacuum, not yout idle screw on the throttle. turn you idle screw so you idle goes up. you are going about it kinda backwards.
But you need to get your timing on. then adjust your Idle speedto where you want it, then adjust your idle mixture screws. you will have to repeat the proccess until you get it right. STart you idle mixture scres 1 1/2 turns out and go from there.
 

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What size cam do you have? Do you have a working choke? If you have an electric choke, you may just need to turn up the high idle. If you have no choke, then its normal to let it warm up before driving.
 

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Discussion Starter #4
Cam is stock for the '71 351C-2V - I don't know how to tell you what it is otherwise. I have an automatic choke, and to my knowledge it is working.
 

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TFOB is right on......

You already have the hard parts replaced to do a tune-up, so you are ready for the fine tuning. Way to go!!!

1. Adjust the timing first.

2. Then, adjust the idle air mixture screws.

3. Then, adjust the idle speed with the screw on the linkage.

4. Re-do the idle air mixture screws.

5. Go back and forth between the idle speed screw and idle mixture screws until you have the fine tuned machine you want! ::

Have Fun!
 

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There is no problem with a slow idle unless your getting a stumble or the engine is running rough. a good stock idle is 800 in P or N and 6-700 in D. If its a manuel tranny then i think its 700. adjust the timming and idle mix untill you get a smooth running enigne. when you do this make sure the engine is at operational temps(a 5 minute drive or a drive around the block twice) worry about the choke after the warm engine is tuned right.
 
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