No you can't change the venturi size, that is the actual size of the carb's venturi and is cast as part of the carb and determines it CFM rating (Cubic Feet per Minute of airflow).
Since this carb was made for a smaller displacement application there is good chance you will never be able to get it run properly as the air bleeds and possibly jetting would be set for a smaller displacement engine. There is a chance this carb will run lean and potentially eventually result in engine damage over time. Today's fuels are already lighter than what was available when this truck was built and require a richer mixture, compound this with a carb meant for a smaller displacement engine and it may lead to trouble, like burned valves sort of trouble.

Your carb is at the very least is the wrong carb, and at worst cobbled together as it is sporting parts from at least 2 different carbs and has been built from who knows what.. There is no way I would leave it in place even if the fuel-air mix is not lean I would change it out for a correct one that has not been pieced together.

Ford 3 speed transmission have a kick down rod that downshifts the trans from 3rd to 2nd when you pin it for something like passing.
This rod is connected to the throttle lever on the carb (see below pic) and the transmission and is what downshifts the trans when you floor it. Only vehicles with automatics had the kick-down lever installed on the carb. If your truck is not auto then it is just more evidence this is not the correct carb. If it is auto then you are missing the kick down rod.

 

Nope my truck is not an auto. Guess I’ll be in search of a new 2100 or 2150 which would be original?


best place to buy a new 2100??

 

Try your local parts houses. O'Reily's lists them for 219 + core. You don't have the correct core but they probably won't notice. I always try to buy things like carbs, starters, alt's etc. from a local source because rebuilds are always iffy and if you get a bad one you just hand it back to them and they give you a new one. Instead of shipping it back to some online seller and waiting two weeks for a replacement.

 

That’s great I have several different ones around me. Do they have the real motor craft carbs or is it just Chinese remakes.

hipefully I can get to one still(this stupid virus has our county shut down)

 

C6TZ-9510-N .. 2100 series Auto-Lite Carburetor / ID tag number: C6TF-T / Obsolete = 1965/67 F100/350 352 M/T

D4AZ-9A586-A .. 2100 series Auto-Lite/Motorcraft Carburetor Kit (Motorcraft CT-499-D) / Available from Ford & auto parts stores.

ALL 1964/74 2100 series Passenger Cars & F100/350; 1966/74 Bronco; 1969/74 Econoline. Comes with gaskets, accelerator pump and check valve, needle and seat, economizer (power) valve.

At one time, all the parts could be bought by themselves. Here are two related to this thread:

C4AZ-9B559-A .. Accelerator Pump (Motorcraft CM-463).

C4AZ-9576-A .. Accelerator Pump Check Valve (Motorcraft CM-825)

Both the pump and check valve should be replaced at the same time.

The check valve fits behind the pump, has a tiny little tit that fits into a hole in the carb body.

 

They should be re-maned Auto-Lite. That's why they want a core back.

 

Okay makes sense. My O’Reillys has non now but autozone down the road has one under the name AutoLine. Is this a good refurb company?

And can I order one online and then bring the carb into the store and get the core without buying one then and there?

 

ASSUMING you have the original factory engine in your truck, what you probably want is the same venturi size carburetor and configuration that was supplied by the OEM. The engineers knew what they were doing.

They all pretty much look the same on the outside but they are not the same on the inside - there are a gazillion different venturi sizes, annular booster clusters, jetting #s & power valve and the rest of it. Anything that will bolt up will start and run, but if you want it to run well then select the correct carburetor to begin with. That's the most important carburetor "adjustment" you can make, by far.

 

Autoline remains are available from RockAuto
The carb I posted a link to IS the correct carb for your truck with a manual from Rockauto. Rockauto is online ordering and likely will be cheaper than AutoZone.
Autoline is a Canadian company that has been around since the late 60's all their rebuilds are done in house and they currently are the best on the market.

 

Take a second and look on the throttle linkage side of your carb down close to the base and it should (might) have some stamped numbers on it. I sort of doubt that says C6TF T since the venturi size should then be 1.14 instead of 1.06.

Another option is to buy the correct original model. One like this.

https://www.ebay.com/itm/1966-352-Fo...8AAOSwsKReXYLb