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Choke and fast idle cam adjustment help
Posted by: monzagal ()
Date: October 11, 2010 04:13PM

Okay so I get the theory... depress the gas pedal... sets the chokes to a "closed" position to enable the car to start.


However in this crap manual it doesn't exactly tell you "how" to adjust the chokes or the fast idle cam...(6M-1) I was hoping for a diagram but there isn't one... can someone pull up a pic of the carb and circle what the heck I'm supposed to be adjusting.. I just don't want to go turning things and jack something up.

I know this is elementary stuff but I need some help..

Thanks

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Re: Choke and fast idle cam adjustment help
Posted by: MrChips ()
Date: October 11, 2010 04:34PM

take a breath!

good.



You are trying to get WHAT to happen that does not now?


The rods that come up from the cylinder head are attached to be-metallic 'coils' just like in a mechanical A/C thermostat in your home.

If they're cold, they try to pull the choke closed.

The choke plate can't move much, though, because the linkage on the shaft is set to NOT let it move unless the throttle shaft has moved at least once. Depressing the pedal rotates the throttle shaft. Through linkage, this makes the accelerator pump squirt some extra fuel in the intake manifold. The choke shaft can now move.

When you let up on the pedal, the throttle shaft wants to return all the way closed, BUT:

Since the choke shaft has rotated to close the choke plate, the throttle shaft linkage cannot close all the way, because the 'high idle cam' (looks like an arc'd linkage w/ notched steps in it) prevents that from happening - the idle speed adjustment screw is supposed to hit that.

At this point: Choke butterfly is closed
Throttle is barely 'cracked' due to the high-idle cam.

you are ready to crank the engine and start things moving.

the vacuum pulloff will immediately 'fight' the spring linkage to open the chokes a bit to allow limited driveability while cold.

As the engine warms up, the springs expand and don't pull on the choke as much, allowing two things to happen:

Choke plate opens fully, allowing a leaner 'run' mixture, as
well as more airflow for WOT operation.

High idle cam rotates out of the way, so throttle shaft can return
to fully closed position (regular idle)


Look for the high idle cam and how it hits the idle screw. Once you've played with it for a few moments, you'll get it!

If I can grab a photo on the way out to work, I will.



Edited 2 time(s). Last edit at 10/11/2010 04:42PM by MrChips.

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Re: Choke and fast idle cam adjustment help
Posted by: MrChips ()
Date: October 11, 2010 05:59PM

Took a couple crappy cel-phone pix for you.

One shows the fast idle cam engaged w/ throttle lever
One shows 'normal' idle position (warmed up).


Grabbed a crappy vidjo, but ran out of space at some point. It's uploading now.

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Re: Choke and fast idle cam adjustment help
Posted by: MrChips ()
Date: October 11, 2010 06:04PM

Crappy and most likely incomplete vidjo here


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Re: Choke and fast idle cam adjustment help
Posted by: monzagal ()
Date: October 11, 2010 08:46PM

Mr. Chips...

You're my freaking hero... thanks for taking the time to do that... now riddle me this... in the morning.. when the engine is cold.. if I blip the accelorator the and pull up on the rods the coils should grab and keep the rods in place.. is that correct..

it appears that my fast idle cam is set correctly.. I'm speculating that my coils might be bad and are not holding my rods in place....

possible?? or not?

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Re: Choke and fast idle cam adjustment help
Posted by: Gregory_Miller ()
Date: October 11, 2010 09:06PM

Those bi-metal coils do age and don't "pull" or "push" as much when old as they do when new...and they are all 40+ years old now! The vendors do sell replacement choke coils, not too bad a job to do, but it requires R&R of your exhaust manifolds, and of course, the lower shrouds. I just did a set last spring for an older fellow who was trying to sell his 65 Corsa. Turned out all his exhaust manifold "donuts" were toast too anyway.

Greg Miller
Eugene, Oregon

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Re: Choke and fast idle cam adjustment help
Posted by: MrChips ()
Date: October 11, 2010 09:11PM

OK.

Assuming then you are popping the hood and 'blipping' the crossover shaft to save time.


When the coils pull down on the rods (Or rather don't push up so much), that opens the choke (or prevents the choke from being closed).

One lazy way to check it is to take a photograph when cold and 'blipped', then re-install the air cleaner, drive the car for the day, then immediately remove the air cleaner again and take another shot from the same angle. This way, you'll see how much travel you actually are getting out of your coils.

There are other methods (Tape a 'flag' to the rod and mark the side of the carb etc..) you can use, but other than the air cleaner, this one's relatively hands-off.

If you remove the lower engine shroud, you can see the coil where it attaches to the head. I had one sitting here at my desk, but took it home last week.



When you rotate the shaft past a certain point, you should see the radial lever w/ the arc-shaped slot that I was first moving with my hand in the video (connects to the rods that screw into the end of the choke coils buried in the heads and directly rotates the choke butterfly shaft) move to close the choke butterfly. If it is not cold enough (hot hot hot summer day) it may not fully close.


Yes, you can crack the throttle a little bit and pull up on the rods (or rotate the lever, it's easier), then release the throttle - that should leave the choke set, and high idle will reign until you've blipped the throttle again. There are multiple 'stages' of high idle. If you're in AZ, you probably don't need to use anything more than the first or second bump.



To adjust:

Swivel/rotate the retaining clip that holds the rods on the lever and pop the rod out of the hole. DO NOT LOSE THE CLIP!

Turn the rod to screw / unscrew it into the rod assembly's threaded coupler. This adjusts the effective length and also sets the 'default' position for the choke lever.

Do this only a few turns at a time. What this does is changes the 'pre-load' on the bi-metallic coils so they can still do what they have to do. If you screw them in too far, your choke may not fully engage, and that's bad juju for starting. Unscrew them too far, and the choke may not disengage fully, and that's bad juju for mileage, carbon deposits, cylinder washdown etc..

Hope I didn't get that backward - it's easier when I can see it in front of me.

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Re: Choke and fast idle cam adjustment help
Posted by: Richard ()
Date: October 11, 2010 11:30PM

Monzagal, if you were rebuilding the carb, you would use Section 6M page -1 through -7. These are the adjustments that you or a rebuilder would do on the bench. All of these adjustments require bending something. It is important to note that rebuilt carbs are not "plug-and-play". There are still adjustments that need to be made to suit the engine they will be run on.
Flip back about 100 pages to Section 6, Engine Tune-up.

The adusments you need are in this Section. While I think the manual is pretty good, they did screw up in Section 6 by going over and rehashing some of the adjustments from Section 6M.

Unless there is a problem preventing you from making the choke adjustment properly, then it should have been covered last month in your other thread.
look at Section 6, Engine Tune-Up 6-7. Half way down the page it says "Adjust Choke (Fig. 15)". Fig. 15 is on the next page.
The adjustment is made by removing the clip from the thin rod and spinning that thin rod in a large arc to thread it up or down. You must be careful as these rods get bent (more than they already are). They must be free to move up and down without dragging.

It says, with the choke held closed, pull up on the rod and it should freely enter the hole in the choke arm. That add two turns. Forget the pulling and forget the two turns. These Choke Coils are 40 years old and some do sag a little. Just hold the choke closed and adjust the rod length until it falls in the hole without pushing or pulling it up or down. Unless there is physical damage they continue to work just fine. There is a decent picture of the coil in Fig. 92, Engine Mechanical 6-43. The head is upside down in the picture, but you can see that the coil/head is cold and the rod is pushed up toward the carb.

The engine speed when the choke is ON (Fast Idle) is adjusted with pliers. The "U" shaped "Tang", resting against the Fast Idle Step Cam must be bent. In order to bend the tang, you will have to screw up the present setting you have for the hot, engine idle speed. I doubt the tangs are off far enough to require that you recheck that adjustment. Best to leave alone.

In the first picture you can see that the bottom, end of the rod has a horizontal section that is trapped in the two curved slots. When the coil heats up, it pulls the rod down to the bottom of the slots. The choke coil is held in place with that twist rivet laying there. I've never removed one on a car and there is no way anyone could get me to if that was the only reason to go in there. I'd set the choke wide open permanently. Getting that rivet to start turning isn't that much fun with the head on the bench.
In the second picture you can almost see the manifold pocket or heat stove the coil sits in to help heat it up. As mentioned earlier, all that has to come off before you start your frustration with the twist rivet.


>>if I blip the accelorator the and pull up on the rods the coils should grab and keep the rods in place.. is that correct<<

As long as the rods are not bent and dragging inside the hole in the head or the linkage isn't gummed up, they should pop up when you blip the throttle. try a small shot of Carb Cleaner or WD40 on the linkage. Make sure the plug wires or anything else isn't under or dragging against any of the linkage.

I know most of this was covered, but I thought I could point to a couple of things.

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Re: Choke and fast idle cam adjustment help
Posted by: MrChips ()
Date: October 11, 2010 11:58PM

Richard, is the twist rivet aluminum?

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