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PostPosted: Sun Nov 17, 2013 6:11 am 
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Javelin

Joined: Thu Mar 28, 2013 9:07 am
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Here is a typical Carter Carb that I did my basic evaluation and tuning to. This first post will be the single most important and critical adjustment to make. We can add more posts about how to make these factory carbs run as well as they should later in this thread.

This carb was put on by a previous owner. It is a new Reman unit about 2 years old. It runs horribly with stalls, dramatic changes in idle speed, and terrible mixture control. To keep it moving at all the throttle screw has been overtightened and good gas mileage is impossible this way. Here is how I fixed it.

I did not bother replacing any gaskets or rebuilding it. I just adjusted it correctly and it runs perfectly now. I started by looking at the driver's side of the carb and pushing the throttle linkage all the way down as far as it will go. This is what I found.

Image

In this picture you will see that the choke plate is about halfway closed. When pushing the throttle all the way down (which is the same as an assistant pushing the gas pedal all the way to the floor) that choke plate must be fully open. This is a huge problem and a very common problem with Carter carbs. Here is another photo of the jacked up linkage where I used my finger to rotate the choke plate to where it should be fully open as I also pushed the throttle fully down. Note the huge space between where the linkage is now and where it should be.

Image

This next photo shows what it looked like when I was done. Compare that to the last photo. I rebent the linkage so that it fully opens the choke plate when the gas pedal is fully depressed.

Image

That linkage is very thin and it will stretch as you drive the car. This linkage is pushing the choke plate open at the same time the choke is trying to push it closed. Especially in the winter when the choke is more aggressive your linkage will slowly bend and change. This adjustment should be checked often and at the first sign of running poorly. To not bother tuning the carb until it has been fixed.


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PostPosted: Sun Nov 17, 2013 6:14 am 
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Javelin

Joined: Thu Mar 28, 2013 9:07 am
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That last post about rebending the choke plate was step one of fixing the carb. Step two is tuning it and setting the idle. Here is how I do it.

1) First I bend that linkage to make sure the choke plate is fully open when the gas pedal is fully depressed.

2) I look at the throttle. This picture shows what I found from the previous owner attempting to tune this Eagle. Notice the spring on the outboard screw is fully depressed, indicating it is overtightened. The inboard screw is overtightened too but pretty close.

Image

3) I back off both of those screws until they no longer touch anything.

4) I push the throttle closed and make sure it does that on its own consistantly. The throttle plate should be as far closed as it can possibly be. Check to make sure nothing is keeping it from going further closed. On this Eagle I found that I needed a stiffer spring and a different spring location in order to pull the throttle fully closed. I had idle problems caused by it not always fully closing automatically when the pedal was pushed and released.

5) I now adjust the throttle screw. This is the outboard screw pictured above that pushes against a solid metal post. First I tighten it until it just barely touches the post. I then go one more half turn or full turn to just barely start to push against the post. Done.

[Note if you get a huge vacuum leak and your car is barely running, this screw can be over-tightened to where it is in the picture. As you do this the car is no longer officially at idle ever because at rest it is running with air and fuel from the throttle bore and not the idle tubes. It is a good temporary fix but never leave the car like this. If your car never idles you will never get better than 20 MPG. You're basically dumping gas into it with a shovel. I find so many cheap Eagles and junk yard Eagles with this single fatal mistake]

6) I next adjust the inboard screw. That is the one pictured that pushes against the rotating choke plate piece. The rotating piece in the picture is metal but most Eagle carbs are plastic. It has steps in it where the one end pushes the throttle open a little bit at fast idle while the car is cold and then it steps down until it isn't moving the throttle when the car is warm. First I hold the plastic rotating piece so that the bottom step is nearest the screw. By "bottom step" I mean the last one it would touch warm, not the first highest step it sits when cold and at fast idle. The screw should be a hair width away from touching the bottom step. It should not touch the bottom step and should just barely graze the second step. It should not do anything at all when the car is warm, only when it is cold.

[Note that this stepped piece is the reason the Eagle owner's manual says that you are supposed to push the gas pedal down once before turning the key. Doing this will let the cold choke push the plastic piece into position so that the fast idle is working when you first turn the starter. When the Eagle is parked overnight the screw can't climb the steps by itself.]

7) I finally go and adjust the idle screws. Those are the two screws down at the bottom of the carb on the front. I start by gently but snuggly tightening those screws as far in as they will go. The blade of the screwdriver probably isn't perfectly horizontal in that position, so I next open them very slightly until the blade is horizontal. That is zero. As I loosen them I count the half turns. I loosen the screws until both of them are 3 full turns (6 half turns) open.

8) I start the car. It will run with a high idle speed. As it is running I tighten the two idle screws to 2 full turns open. Most of my cars idle with either 1-1/2 turns open or 2 turns open on the idle mixture screws. Starting the car with 3 turns is a good idea because I just want to know for sure it will start the first time I turn the key. I always set the final value with the car already running anyway, I may as well start it at 3 turns.

[Note that in the car pictured I ended up at 2 turns and it runs beautifully but the idle RPM flutters a little bit. This car has major vacuum tube spaghetti and several leaks. The last Eagle I adjusted did the same thing until I ripped it all out and replaced all the vacuum lines. At that point this car should idle smoother and lower at 1-1/2 turns on the mixture screws]

9) I adjust the accelerator pump lastly. This is a common problem with the Carter. As it is running warm I pop the top cover off and find two set screws affecting the position of two levers relative to a rod. I make sure the accelerator pump is almost as far as it can go up but not quite against the limit of the adjustment. I have found a bunch of Eagles where people turned it all the way down and essentially disabled the accelerator pump from working. This is a common mistake by people who overtighten their throttle screw and never idle using the idle mixture tubes. In that condition you're dumping gas in the carb so fast you will actually lose power if the accelerator pump fires off, so people turn it off. Now that the throttle is back to where it should be the carb is running totally on the idle tubes and barely sipping any gas. The accelerator pump is very necessary to push a shot of gas when the pedal is first depressed to smooth out the transition from idle to throttle.

I know the accelerator pump is working correctly when I check to make sure the engine RPM changes smoothly and evenly both with the pedal is pushed slow and the pedal is pushed fast.

That's it. I declare it fixed and drive it for a couple days to see how it runs cold and hot. I don't even bother with a vacuum gauge anymore unless I'm checking timing, which I usually don't bother with. I just do this and the Carter's run great for me. I rarely bother cleaning them and nearly never replace gaskets. They've been tough, cheap, forgiving carbs considering my neglect. If I need to remove a Carter carb for cleaning I will be bolting a TBI back in instead.


Last edited by captspillane on Sun Nov 17, 2013 7:15 am, edited 3 times in total.

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PostPosted: Sun Nov 17, 2013 6:16 am 
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Javelin

Joined: Thu Mar 28, 2013 9:07 am
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Step three is basically a carb cleaning. If the Eagle isn't running right I first rebend the choke linkage. Next I tune it. If it still isn't working right I pull it off and clean it out. I'll post pictures by editing this post in the future.


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PostPosted: Sun Nov 17, 2013 2:09 pm 
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Javelin
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Location: Royersford, PA
Thanks for this! Not sure about bending that linkage on mine though, I tried and it stayed at high idle even when the car was warm. The plastic piece would no longer move down any further on its own when the throttle was depressed.

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PostPosted: Wed Dec 11, 2013 6:50 pm 
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Javelin

Joined: Sat Apr 06, 2013 10:51 am
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Location: Oshkosh, Wis.
Thankyou I will be checking this as soon as I can

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PostPosted: Thu Mar 20, 2014 9:41 am 
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Noob

Joined: Wed Oct 02, 2013 7:34 pm
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The fast idle cam needs to be completely free of dirt and grime so it can rotate on that shaft freely. With the engine off and the throttle opened up fully, you should be able to hold the choke open and the fast idle cam/linkage should lift and drop back into place on it's own every time. My '86 was gunked up so bad the cam would stick and the car would stay in fast idle and race.


What I don't understand is the manipulation of the choke linkage. Is this done to prevent the issue of poor hot starting, where the choke has cooled prematurely, before the engine? I would think that upon turning the engine over, the choke vacuum pull-off would activate, giving the engine enough air to get going again. The fast idle cam should drop completely away from the fast idle set screw when the engine reaches normal operating temperature. Bending that linkage to an extreme may cause the cam to stay in the loop all the time. I've just never read about such an adjustment and it takes a good amount of force to bend that linkage. From what I understand, hot starting issues can be caused by the wrong fuel filter pushing unused gas into the carb during a hot shut off, flooding the carb. I agree that when the gas pedal is pushed to the floor, the choke should open some amount, just not all the way.


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PostPosted: Thu Mar 20, 2014 4:04 pm 
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Hornet
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Location: North Seattle sort of
On some the linkages were messed with, often by well meaning "mechanics" that lead to issues.

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PostPosted: Fri Mar 21, 2014 1:00 pm 
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Noob

Joined: Wed Oct 02, 2013 7:34 pm
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I agree the choke plate should open when the throttle is wide open, but I don't think it should open all the way. Should be something like 3/32" according to the rebuild sheet.


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PostPosted: Wed Nov 30, 2016 7:19 pm 
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Are there any pics of the accelerator pump adjustment? Or a little more detailed description? I'm trying to get mine tuned but I'm not sure which adjustment affects what. It looks like there are 2 adjustments to make.

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