The Stovebolt Site Forums The Shop Area Engine Shop Need help- Carter W-1 carbs

I have been starting to fashion together a 2x1 set-up for my 292. I am straying from the typical mono-jets and opting for the more vintage look of the carter W-1.

As a result I have been collecting several W-1 carbs trying to restore the best ones to use.

Here's the thing though. I have 4 at the moment. Two of them have vertical linkages that go from the throttle shaft to the choke shaft. These ones apear to close the throttle butterfly when the throttle shaft is pushed in a direction that would indicate acceleration.

The other two I have do not have the vertical linkage, and as expected open the throttle butterfly when the throttle shaft is pushed toward acceleration.

So I'm kind of at a loss here trying to figure out why some would close while others would open with the same model carbs. I'm thinking that maybe it was a difference in thottle linkages maybe? Can anyone explain the difference to me and point me in the right direction?

Thanks.

When you mention a link, I assume that you’re talking about the fast idle link and this model: http://rides.webshots.com/photo/2829647430098611668HBDljd
It's a W-1 model 684 from 1949; the earlier models did not have this fast idle link. It has an accelerator pump that is spring-loaded from the top, which forces the throttle open. The earlier W-1’s had an accelerator pump that was spring loaded from the bottom, which kept the throttle closed.
Jon aka carbking is the man to talk to about this and if you stay with it he may chime in with the real skinny on this application.

Denny Graham
Sandwich, IL

That is the linkage I am talking about. I am wondering if they are needed, and if not, is there I way I can successfully modify them to be the other way?

Is there an advantage to one version over the other?

I hope "carbking" chimes in. That would be nice.

Thanks.

Like I said before, that link is just the fast idle link, when you close the choke the cam just holds the throttle from closing all the way to idle. As far as reversing the accelerator spring, no you can't change that.
If your veering from a stock set up I'm afraid I can't be of any help, I'm not a design engineer.
Denny Graham
Sandwich, IL

As Denny suggested, the fast idle link from throttle to choke identifies the carburetor as the 684s. The 684s was the last of the production W-1 carburetors, and, as such, incorporated ALL improvements, modifications, etc. and, all things equal, would be the very best of the W-1 carbs.

Unfortunately, all things are not equal, and since the 684s design was only used one year, many parts are less available than the other models, and some are quite expensive.

I personally do NOT like the spring on the top of the pump, but just personal opinion.

Jon.

I'm just confused as to the operation of the thing. It makes no sense to me to have a butterfly that closes when the throttle is opened. Unless, I'm missing something and that there is a difference in the way the throttle is supposed to be hooked up or something.

I've got plenty of parts for them, just want to know why the dang thing works. I'll run them if they are the best of the W-1s, but I do like the earlier style better, if only because their operation makes sense.

Would anybody feel that the early version of the YF would be a better way to go than the W-1? I've heard that the Rochester Bs tend to be a pain.

I'd like to keep a vintage looking Carb. The mono-jets do not look at home.

Thanks.

I think your confusing the accelerator spring pressure with the throttle return spring. It is not a throttle return spring it is the pump operation spring.
In it's original configuration on the 1949 216 the throttle return spring that is connected from the vertical linkage to the clip on the pan or bottom edge of the block, over came the accelerator spring pressure and held the throttle butterfly in the closed or idle position. If the throttle return spring or any other part of the linkage were to break or come loose the W-1 684 would have gone to full throttle.
It’s probably a good thing that this setup was only around for one year before being replace in production with the Rochester 'B' carburetor.

Denny Graham
Sandwich, IL

The operation does make sense. As one closes the choke butterfly (the one at the top), the linkage is designed to slightly open the throttle butterfly (the one at the bottom). This is consistant with the operation of most automatic chokes except most automatic choke also have a stepped fast idle cam.

The purpose of this linkage was to slightly speed up the engine (a fast idle) when the choke was pulled. Most manual choke carburetors do not have this provision.

Jon.

Perhaps I am confusing the throttle spring and the pump spring, but still don't get the concept. The shaft and link that I would assume connects to the accelerator, when moved appears to shut the throttle butterfly closed. Most carbs I have seen open the throttle butterflys when when the trottle is pushed.

On my carbs the throttle butterfly is held open normally without any pressure on the throttle shaft linkage. Once you startint to turn the throttle shaft immulating acceleration and resisting the spring pressure, the throttle butterfly closes.

Maybe I'm missing the throttle return springs or something? I just can't figure out why a throttle butterfly would close at you are moving toward WOT.

So I guess I'm still lost....

Hopefully this really bad drawing will show up and help explain what is happening. It is based on the picture that Denny linked to above. As I move the throttle shaft linkage in a counterclockwise direction indicating acceleration, the throttle butterfly is closing.

[img]http://i18.photobucket.com/albums/b117/hotrodderguy/carb.jpg[/img]

If this is correct, how would less fuel+air accelerate the car/maintain a higher speed?


.

Take a look at this one:

http://www.thecarburetorshop.com/Carter684s.jpg

Jon.

In the preceding, as the choke arm (top) is pulled from left to right to close the choke butterfly, the extension of the choke arm pulls the vertical slotted rod to the left. This motion causes the idle screw (to the left on the throttle arm - bottom) to rotate, which partially opens the throttle, and speed up the engine.

Jon.

By the way, two of these would be marginal for a 292, 3 would work much better. Use solid linkage.

Jon.

So, ignoring the choke altogether..... Should the throttle butterfly be closing as the the throttle arm is being rotated counterclockwise? And if so how is the air getting passed the throttle butterfly while it is closed at WOT?

The other models I have without this linkage have the throttle butterflys opening when the throttle linkage is being rotated counterclockwise.

I think I know what is going on, but want to be certain. I'm thinking that the springs that are supposed to "resist" the throttle spring/pump spring are missing or shot. Because on the carbs that are pictured above the throttle arm is pointing to 4 o'clock and and the idle screw is touching the choke rod at about 3 o'clock. On my two carbs the throttle arm is pointing to 1 o'clock and the idle screw is not in contact with the choke rod, it is pointing at 12 o'clock with the slotted head of the screw pointing downward at the base. (wish I had a camera right about now)

So I'm guessing that I have a couple bad or missing springs?

NO!!!! The "throttle" butterfly does not close as it is rotated in the CCW direction! If you rotate the arm that you have drawn in the CW direction the idle stop screw stops against the fast idle link. If the arm is rotated CCW the idle scerw comes off of the link and the throttle butterfly opens, feeding more air and fuel to the engine.
Your drawing shows this, the picture I linked you to shows this and the picture that Jon linked to shows this.
Not sure just where your having a problem seeing this?
Denny Graham
Sandwich, IL

The trouble is the initial condition and placement/position of the throttle arm/butterfly. I do not have a model to go off of since it appears that both of my models are messed up. So with out help from you all I can't tell what is normal.

The idle screws on mine are already off the fast idle link. Which is telling me that something must be wrong with both of them. I can not move the throttle arm in the CCW direction from where the throttle arm rests normally, only CW and then the throttle butterfly closes tight. There is spring tension when I rotate CW. There is no tension of any sort holding the idle screw against the fast idle link. In fact at rest the end of the idle screw is pointing directly upwards. I'm trying to figure out why this is and what can be done to get them back to the way they should be with the idle screw against the fast idle link. I have had them apart several times, followed diagrams and the only spring that I see involved with positioning of the throttle arm is the pump spring. So if the pump spring is correct and in the proper position, what else might cause the throttle arm to start with the idle screw pointing upward and the throttle arm pointing at 1 o'clock while at rest?

This is all I'm trying to get to the bottom of. I thank everybody for their time, patience, and experience. I just wished that I had a camera to show what I am trying to describe.

Below is a drawing of what mine are like:
[img]http://i18.photobucket.com/albums/b117/hotrodderguy/carb-1.jpg[/img]

Yes! Normal for the Carter W-1 684 carburetor is WIDE OPEN butterfly or FULL THROTTLE, because of the way they designed the accelerator pump spring. Do you understand that the accelerator pump is a part that is inside of the carburetor and there is a spring that is inside the carburetor that pushes down on the accelerator pump? Then follow the linkage and you will see that if the pump is being pushed down that it is going to hold the throttle open.
The pump spring pressure is overcome by the greater spring pressure of the throttle return spring when the carburetor is installed on the engine.
Last picture:
http://rides.webshots.com/photo/2834205070098611668DlZRNd
Denny Graham
Sandwich, IL

Thanks, That is what I was trying to get to the bottom of. The return spring solves it all. I have never seen one of these installed before and did not know if it was a stand alone unit with the throttle butterfly normally closed.

I've had them apart and understand the insides. Just not that there was to be an additional external spring (return spring) that was an integral part of the system.

I appreciate the patience in trying to help me get to the bottom of this. I knew it had to be something simple, but communication was tough. Thanks again for your help.