Carb tuning question..

[Anonymous]

I recently rebuilt the factory Autolite 1100 on my '66 Mustang 200 automatic, and I set all the initial settings per the shop manual. Only the idle speed and idle fuel mixture have been tweaked slightly from the initial settings, and it runs well in general.

My problem is that although it idles well, when I just start to press the throttle, it tends to sputter. If it makes it past this to a higher RPM, it runs great, until I have to come back to a stop and go through the extremely light throttle section again.

What could be some possible causes of this behavior? Is this the "flat spot" that the 1100s are notorious for having?

 

[Asa]

it sounds like the accelerator pump is not adjusted correctly
there should be a little arm on the side of the pump with a screw that pushes on a diaphragm, that's what needs adjusting

 

[CZLN6]

Howdy Daniel:

The transition bog you are describing is either a lack of initial advance or (And- it could be a bit of both) the accelerator pump is not working adequately.

I forget your location/elevation, but you should have at least 12 degrees of initial advance for a stick trans, or 15 for an auto.

To check the accelerator pump function, located on the right side, remove the air cleaner, prop open the choke and have someone depress the accelerator. You should see a squirt of raw gas into the carb throat. If you do not you have discovered your problem. There are two adjustments on an 1100. One is determined by a rolled pin in the lever on the side of the float bowl. The two holes are marked "H" and "L", which refer to high (leaner) and low (richer) elevation. I seem to recall that FoMoCo used 3,500 ft as the demarcation point, but try both to see what results you get. The second is the right angle bend in the rod that goes under the bowl to the pump arm. Straightening it slightly, making it longer will length the pump diaphram travel, to a point. This is a very small adjustment, and best done with the bent rod removed. DON'T over do this one.

If this doesn't get the bog gone you will need to re-rebuild the carb with particular attention to the accelerator pump function. Make sure all the check balls are in their proper location(s) for the pump to work right.

The diaphram on the engine side is for engines with auto trans only. It is an anti-stall dash pot. It can be adjusted with the threaded bolt asa67 refered to if you have the auto trans version.

Adios, David

 

[Anonymous]

Wow! Thanks for the informative replies!

I'll take a look at it this weekend, starting with the timing, which I haven't checked in quite a while.

Thanks again!

 

[Anonymous]

also make sure to check that the vac advance is working properly- with the light on it rev it up and you should see the light "walk' around advancing the timing. I had a bad diaphram on my 62 and it would acrually work backwards. $12 part made huge difference.