Vintage Mustang Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
146 Posts
Discussion Starter #1
I finished rebuilding my 4100 last night installed it this morning and it runs great. Still need to do some fine tuning with the choke. It seems that I may be missing some linkage that controls the secondaries. When the primary throttle is open all the way there is no connection to the secondaries to allow them to open. I do not have a manuel that shows a picture of the choke side of the carb to see what I am missing. Can anyone help with a picture or discription.
Thanks
Phil
 

·
Registered
Joined
·
3,894 Posts
The secondary linkage on the 4100 is on the same side as the choke. It runs from the rear of the carb (where the secondary diaphragm is) to the secondary butterflies. There is no manual connection to the primary butterflies.

The primaries must be opened to allow the secondaries to open. If yours will open without the primaries being opened then you have an unsafe condition. On the passenger (choke side) there is a small pin that pulls the secondaries closed when the primaries are closed. This pin prevents the opposite as well. Many times it is inadvertently left off creating this condition.
 

·
Registered
Joined
·
10,587 Posts
I'll get a picture off the D-coder and post it to my site in the morning...remind me if I forget..*G*

If the description already provided serves your purpose, disregard...
 

·
Registered
Joined
·
146 Posts
Discussion Starter #4
Charlie, I may need to get a article on how carbs work. If there is no linkage how do the secondaries work?
Phil
 

·
Registered
Joined
·
63 Posts
Venturi vacuum through tubes in the carb body, to the diaphram-spring / actuator rod at the rear of the carburetor, which then opens the secondary throttle plate.
 

·
Registered
Joined
·
3,894 Posts
See the little tube sticking into the primary venturi on the drivers side? That is the pickup for the secondaries. It is ported back to the secondary diaprgam along the top of the carb (you can see the ridge cast into the top).

As incoming air accelerates through the venturi the pressure drops (Bernoulis law). This pressure drop is sent to the secondary diaphragm and pulls it open. The beauty of the design is that it opens when the engine can use the extra airflow and not before.

When the accelerator is closed, the pressure rises in the venturi and the spring inside the housing on the backside of the diapraghm closes the secondaries. (there is also a mechanical stop on the throttle linkage that will pull it closed too (that's the one I mentioned before).
 
1 - 7 of 7 Posts
Top