high Idle 318

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Dakota R Keck

Dakota R Keck

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Location
Ada Oklahoma
I have a 73 dart custom with a 318 carter 2 barrel that idles very high until i fiddle with the fast idle cam. I have adjusted every thing according to my service manual and it always reverts to the same issue. The carb was rebuilt new gaskets and all new vacuum lines through out. I daily this thing and it gets annoying having to take the air cleaner off daily lol
 
Dakota R Keck said:
I have a 73 dart custom with a 318 carter 2 barrel that idles very high until i fiddle with the fast idle cam. I have adjusted every thing according to my service manual and it always reverts to the same issue. The carb was rebuilt new gaskets and all new vacuum lines through out. I daily this thing and it gets annoying having to take the air cleaner off daily lol
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Hello Dakota R Keck,
Kinda hard to diagnose with the information provided.
If possible take some pictures of the carb (both passenger and drivers side) before you start it (cold) and after it warmed up But before And after you have to fiddle with it.
Post them here when you get them.
This may help us help you.
Happy Mopar :)
Arron
 
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Dakota R Keck said:
I have a 73 dart custom with a 318 carter 2 barrel that idles very high until i fiddle with the fast idle cam. I have adjusted every thing according to my service manual and it always reverts to the same issue. The carb was rebuilt new gaskets and all new vacuum lines through out. I daily this thing and it gets annoying having to take the air cleaner off daily lol
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After it has warmed up for a few minutes try giving the throttle a quick blip, most times that will get it off the high idle cam.
 
Need more info. What does "fiddle with the fast idle cam" mean? Are you saying that the cam is still engaged and not allowing the carb to return to curb idle? If so, then the linkage is out of adjustment or the choke is not fully opening.
 
It more sounds like a choke spring, choke arm adjustment problem not letting the choke open fully. How does it act if you disconnect the choke arm link from chockewell from the carburetor ?
 
Agree with Arron tate about taking photos, it sounds like the fast idle cam is not free to move or the linkage is installed wrong.

here is a photo of my 67 BBD
20190309_074631.jpg

and a second photo of a 66 or 65 (not sure) and earlier BBD
20190309_074855.jpg
 
Murray said:
Need more info. What does "fiddle with the fast idle cam" mean? Are you saying that the cam is still engaged and not allowing the carb to return to curb idle? If so, then the linkage is out of adjustment or the choke is not fully opening.
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The fast idle cam is staying where it idles high i have to adjust it to where it isn’t idleing super high. If not adjusted it idles high and diesels. Once adjusted it runs great i was more or less trying to figure out the culprit, i daily this thing and this is my only issue and i dont want her laying down on me.
 
Dakota R Keck said:
The fast idle cam is staying where it idles high i have to adjust it to where it isn’t idleing super high. If not adjusted it idles high and diesels. Once adjusted it runs great i was more or less trying to figure out the culprit, i daily this thing and this is my only issue and i dont want her laying down on me.
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Assuming the fast idle cam can fall down by gravity as it should when the choke is fully open then the idle speed is controlled by the other screw that stops on the large fat screw on the carb.


Some photos of your carb would be really helpful both left and right sides


shot in the dark... the distributor advance is pulling in too soon and speeding the engine up.
 
It should fall into place by gravity when the choke unloads completely. Is it tight on the shaft? Are you loosening the mounting screw to make it fall into place? Does the screw have a shoulder or sleeve on it or is it binding the cam into place?
 
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Another long shot, make sure the vacuum break line isn’t stopped up or restricted.
 
both of your idle screw looks way to screw in to me. look at my photo in post 6. Also your normal idle screw looks like it was ground down.

When your choak is fully open and the throttle is fully open does the weighted fast idle cam fall down by itself or do you have to force it to move
 
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Dana67Dart said:
both of your idle screw looks way to screw in to me. look at my photo in post 6. Also your normal idle screw looks like it was ground down.

When your choak is fully open and the throttle is fully open does the weighted fast idle cam fall down by itself or do you have to force it to move
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The pic above is where it is when the choke is open or closed and when it acts up
 
IMHO. if you have to have your idle screws in that far to idle than you carb needs rebuilding as it suggests the idle circuits in the carb are clogged OR you don't have the idle screws out enough. Assuming the idle cir is plugged you would need to open the butterfly more to compensate. a vacuum leak might also cause the same situation.
 
The carb was supposenly profeesionally re built when it was purchased the guy furnished a reciept, maybe it wasnt done correctly, ill talk to my brother about rebuilding it and go from there
 
Im confused...

How the choke / fast idle linkage is supposed to work.

1. the thermostat (heat riser) pushes up on the choke lever on the pass side of the carb when the engine is cold.
2. the choke closes
3.the choke rod pulls up on the weighted fast idle cam.
4. before you start the car your press the gas pedal down this allows the weighted fast idle cam to rotate counterclockwise.
5. when you release the pedal the fast idle screw comes to rest on the fast idle cam increasing the amount the butterfly is open
6. after the engine starts and heats up the choke thermostat ( heat riser) pulls the choke lever down and the choke opens.
7. when the choke opens it rotates clockwise allowing the weighted fast idle cam to fall by gravity out of the way.
8. the normal idle speed screw takes over and the car runs and normal slow idle.
 
Let me reiterate that your idle screws are screwed way to far in. look at my photo and your photo for comparison..


AND please answer this question....

With the choke held open and the throttle held fully open is the weighted fast idle cam free to move. IE if you rotate it counter clockwise does it fall back into the most clockwise position with out any assistance
 
4360D984-34F1-43B8-B251-C2B154859248.jpeg
Dana67Dart said:
Let me reiterate that your idle screws are screwed way to far in. look at my photo and your photo for comparison..


AND please answer this question....

With the choke held open and the throttle held fully open is the weighted fast idle cam free to move. IE if you rotate it counter clockwise does it fall back into the most clockwise position with out any assistance
Click to expand...
It stays in the position where it is in the photo
 
Also just for the sake of it, the last photo in post 11 shows the front stud nut almost completely off thats because you had the carb off earlier and haven't bolted it back on yet?
 
The vacuum choke break is the pot with the link on the choke spring side of the carburetor, it has the vacuum hose coming out of it to the side vacuum port on the carburetor. It balances choke opening by the amount of vacuum under the choke to keep the choke plate from staying completely shut.
 
One last thing, my 67 sat for 4 years without being started. I sprayed some starter fluid down in the carb and the darn thing started and kept running. I got it smogged and it passed, i then decided to rebuild the carb and didn't need any tools to remove the carb or unscrew the screws to dissembled the carb. the gaskets has shrunk up that much.

The reason I say this is that he carb is super simple and reliable and easy to rebuild. just take LOTS of photos as you dissemble it. and watch for check balls etc. dont try to take out the screws holding the butterfly or choke plate in. also if you have a CAP carb the idle screws might have a hidden set screw that will have to be removed before you can unscrew them or you WILL break the idle screws and that is a ***** as they are not reproduced ( ask me how I know!)
 
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