Here is the statistical information -
1974 F-100 360 FE 2bbl Motorcraft Carb (Rebuilt)

So...I have searched and read, and searched and read, and I still need a little clarification. I think I am having trouble with my fast idle cam. I have set the cam using FMC400's instructions from another post. However, I still never get a "fast" idle. It doesn't appear the cam ever engages anything other than a tang that moves the choke plate (under the adjustment screw that is situated in the white plastic piece on top). I don't see it engaging the throttle in anyway. I wonder if someone can put a picture or something as to how it should look?

Here is the way I understand it's operation (which may be the problem, I may not understand correctly, it may work exactly how it is supposed to). . .

I live in central AL and the ambient temp here is around 75-80 during the day. So, I realize, the warm up is not going to take near as long as 20 degrees. However, the choke does still engage on my cold engine (left overnight for example) and takes anywhere from 5-10 minutes to fully open. If I understand correctly, even on a warm day, if I push the accelerator to the floor this should engage the fast idle cam to the highest idle position. Then, if I feather the accelerator, or the choke begins to open (whichever is first), the cam will move to the second detent. Then when the choke fully opens the cam will move to the last setting - curb idle. What should be "moving" from position to position? Is it the stationary screw that is on the back of the assembly (screw head facing the firewall and slightly down)?(This is the screw that I aligned with the "V" notch on the cam). Or the screw in the white plastic thing?? Or what??

Bottom line - I have never been able to make the truck fast idle. If I push the accelerator to the floor it idles the same as if I just cranked it without touching the pedal.

Am I right to think it's not working? Or will it only engage if it is REALLY cold??

Anyone who can shed some light, I would really appreciate it!!

 

This doesn't look good. Usually someone has some input pretty quickly. I am SO not versed in the workings of this old carb/choke system.

Hopefully I am over thinking this thing!

 

Yes, even on a warm day, provided the engine & choke coil are cold, the cam will drop when you press on the accelerator & set the fast idle.......this is assuming the bi-metal coil is working properly & closing the choke (is it?).

As the choke begins to open, the cam can only shift (lowering the idle), when the accelerator is touched.

The 'part that moves' is the cam with the V-notch on it. The speed & distance it moves, is governed by the travel of the choke itself, as the choke coil warms up. The screw in the white plastic arm sets the choke & cam to each other (important).

The screw that you aligned with the 'V' is attached to the throttle shaft, & is to adjust the idle, but only while the choke is still on. As it sits on the different steps of the cam, the idle changes.

Once the choke is wide open, the cam tips away & that screw no longer touches it. The screw on the other end of the throttle shaft (drivers side) adjusts the curb idle when the choke has opened.


These links might help -

http://repairguide.autozone.com/znet...528004e0d9.gif

International Full Size Jeep Association

The instructions you want are near the bottom of the page, but the choke pull-off measurement he gives, may not suit your engine.

 

Thanks Ken!

Yes, the choke is closing and cold engine when I was looking at it. I made sure to check it after it sat overnight. The picture you attached helped. I didn't understand the way the cam and the screw interfaced. I thought the notches on the cam would "catch" on something. Now that you have eplained the cam "drops" I think I've got it. If I understand the picture, the top of the cam (being wider) pushes the screw on the rear of the linkage toward the firewall, which pulls the throttle linkage towards the rear of the carburetor (idling the engine up). Then as the cam rises(from the choke opening and depressing accelerator) the screw rests on the second less wide section. Then finally, the screw rests on nothing as the cam falls completely away. Do I have it now??

My screw on the back doesn't even touch the cam. So, I believe it needs to be adjusted in toward the cam. The carburetor is a rebuilt from National Carburetors and was supposed to be bench/engine set at the factory. I assuemed that meant EVERYTHING, including this setup. That's what I get for assuming!

I know this seems like a simple thing for me to not understand, but this is the first vehicle I have ever owned with a carburetor. I really appreciate the help getting it straight!

 

You've got it!

I guess your curb idle adjustment is OK, so if (with a cold engine) you press the accelerator down & release it to set the choke, you can then turn the screw (in the pic) inward to touch the highest part of the cam, then add another turn or so. That will at least give a good start point to go from, & can be adjusted from there.
The first time that you tap the accelerator after starting, the cam will shift & the screw will sit on the 'V' to begin warm-up.

It's probably worth checking the choke pull-off setting, the fast-idle cam linkage (that's the 'V' notch setting), & the choke cap setting.......to be sure they are all OK.
The pull-off adjustment needs to be done first, because changing it also affects the fast-idle cam adjustment.

It can all take some perseverance.......partly because the engine needs to be cold to know the results of your last adjustments; also, if you don't know the exact specs for your carb's pull-off, you might need to experiment a bit there too.
If you have a Chiltons manual, & the carb's original tag, you should be able to get all the proper settings to start from.

BTW-The choke pull-off should be measured at the lower edge of the choke flap (some literature says the top edge, but is not correct).

Good luck!

 

How did it go?