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Discussion Starter · #1 ·
I finally got my 72 gt running, but her idle speed was somewhere between 2 and 3000. My dad tried adjusting timing and adjusting some screw in the carb but he couldn't get it lower without the engine dying.

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Über Genius
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What carburetor?
Picture will help
 

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Could be a problem with the advance mechanism in the distributor.
 

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Can Opeler
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You were possibly turning the mixture screw instead of the idle screw. You adjust the idle with the (3/8”?) hex screw pictured here.

The idle mixture screw is for correcting your Air fuel ratio at idle (ie leaner or richer) to get this one close screw it all the way in and then screw it out 1.5 turns.

Make sure your vacuum lines are all connected properly. A massive vacuum leak can cause the car rev that high. Make sure the brake booster hose is connected on both ends and not leaking.

Make sure the throttle linkage isn’t stuck.

Most likely you just have the idle speed screw wrong. Loosen it until it doesn’t touch the throttle levers, then tighten it to where it slightly touches. Try to start the car (it may not run, but it will likely run really slow like a tractor) then keep tightening the screw until you get to the idle you want. After that let it warm up, drive it if possible and recheck the idle speed. It will change after the engine gets warmer.




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Discussion Starter · #7 ·
You were possibly turning the mixture screw instead of the idle screw. You adjust the idle with the (3/8”?) hex screw pictured here.

The idle mixture screw is for correcting your Air fuel ratio at idle (ie leaner or richer) to get this one close screw it all the way in and then screw it out 1.5 turns.

Make sure your vacuum lines are all connected properly. A massive vacuum leak can cause the car rev that high. Make sure the brake booster hose is connected on both ends and not leaking.

Make sure the throttle linkage isn’t stuck.

Most likely you just have the idle speed screw wrong. Loosen it until it doesn’t touch the throttle levers, then tighten it to where it slightly touches. Try to start the car (it may not run, but it will likely run really slow like a tractor) then keep tightening the screw until you get to the idle you want. After that let it warm up, drive it if possible and recheck the idle speed. It will change after the engine gets warmer.




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I've turned the idle speed screw as far as it will go and it's not even touching the throttle lever

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Can Opeler
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I agree with above. You almost certainly have a massive vacuum leak unless your chokes fast idle is stuck on somehow.
Get some carb cleaner, start the car and spray around the base of the carb, the intake, all hoses, and the brake booster. If idle drops suddenly when you spray at any of these location then you have a leak there.


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Discussion Starter · #11 ·
I agree with above. You almost certainly have a massive vacuum leak unless your chokes fast idle is stuck on somehow.
Get some carb cleaner, start the car and spray around the base of the carb, the intake, all hoses, and the brake booster. If idle drops suddenly when you spray at any of these location then you have a leak there.


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When my dad was trying to adjust the idle I think he was messing with the idle jet screw which seems to have had an affect on the throttle lever. When I loosened the idle jet screw slightly the throttle lever moved to where it was touching the idle speed screw

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Can Opeler
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If he was messing with this screw he may have gotten the choke stuck on and you may have just released that screw from the cam that engages fast idle when then the choke is on.
Check and make sure your choke plates are open like this next picture. And then try to start the car



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Über Genius
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As I said... pictures.

Yes, pictures of the carb. Without the air cleaner on it.

What's going on is you are trying to adjust the carb with the choke engaged. This is not going to work and we won't be able to help because we assume you don't have the choke engaged.

I'm not trying to be mean but if you say you don't know much about cars, we will have to ELY5 for you.

You have three adjusting screws on the carb. One is choke idle plate setting. You adjust that one when the choke is engaged but ONLY after adjusting the other two.
One is an idle plate setting and the other is an idle air mixture.


In the picture above, that's the choke idle plate adjusting screw.
 

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Discussion Starter · #14 ·

If he was messing with this screw he may have gotten the choke stuck on and you may have just released that screw from the cam that engages fast idle when then the choke is on.
Check and make sure your choke plates are open like this next picture. And then try to start the car



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How do I get the choke to stay open like that?

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If it's an electric choke then the choke would stay open after power has been applied to the choke for about 2-4 minutes.
Then you open up the throttle and the choke should pop open.
 

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Discussion Starter · #18 ·
If it's an electric choke then the choke would stay open after power has been applied to the choke for about 2-4 minutes.
Then you open up the throttle and the choke should pop open.
I can't really get the car to run for that long though. Is there a way to open in manually?

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I can't really get the car to run for that long though. Is there a way to open in manually?

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It doesn't have to be running. Just have power turned on.

But to open it manually, just take off the air cleaner, open the throttle, open the choke plate. Easy peasy.
 

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Discussion Starter · #20 ·
It doesn't have to be running. Just have power turned on.

But to open it manually, just take off the air cleaner, open the throttle, open the choke plate. Easy peasy.
Okay, so it I understand correctly I should be making adjustments to the idle mixture and idle speed screws with the choke open. Once I've adjusted those, then adjust the idle plate setting with the choke closed?

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