Correct carburetor

[delli]

Hi,
First time posting on this forum and newby Shelby owner. I recently purchased a 1966 GT350H #1264. It has an automatic transmission. I do not have the build sheet. It is in rough condition (bullet holes in the panels and frame rust in the rear frame) It is also missing the carburetor. I have been getting conflicting answers to what is the correct carburetor.  I realize it is an Autolite 4100 and is rare and expensive. So my questions are:

     1. What is the correct carburetor?
     2. Any leads to where I can find one?

                                                 Thank you!

[6s1640]

Hi Delli,

Welcome to the SAAC Forum.  Hopefully there will be lots for you to learn and share.  The correct carburetor is the C6ZF-9510-F Autolite 4100 with integral manual choke stop.  The driver side forward ear will be stamped 6Z F.  As you said, are very hard to find these days.  The manual tran carb is C6ZF-C, which are easier to find.  The functional difference is the size of the jets and venturies.

Please share an image of your car.  We would love to see.

Best of luck

Cory

[S7MS427]

delli,

You are chasing the holly grail of Autolite carburetors.  The one you are looking for is a C6ZF 9510-F.  Scarce as hens teeth and can cost as much as $5,000 (maybe more, I haven't checked prices lately).  The Hi-Performance 289 carburetor for a manual transmission car is a C6ZF 9510-C and is much easier to find.  The C6ZF-F carb is so difficult to find, that I had  to settle on a C6ZF-C on my own car and add a dashpot (which is the only difference I can find, although others may have more information.

There is a vendor who sells on Ebay who seems to get them occasionally, Gotta Fish Carburetors.  I don't have any knowledge of his quality of work and I am not affiliated with with this vendor.  Other than that, I don't have any information as to where you might find one.  Best of luck in your search.

[delli]

Cory and Roy,

    Thank-you for your quick and thorough answer. I now have the information to start my hunt for a carburetor. I will send pictures in the next few days.

            Sincerely, Kevin

[6s1640]

Hi Kevin,

Glad to help.  Attached are images of the two venturies from a C6ZF-F carb.  The "BA", secondary, is more common and can be found on other applications. There are three on a popular auction site right now, one even NOS.  The tough one is the "M" or "MA", primary.  It appears to be unique to the HiPo carbs.

According to Tony Gregory from "The 289 High Performance Mustang" third addition, the jets are sized as:

C6ZF-F  50F primary, 69F secondary
C6ZF-C  52F primary, 68F secondary

I should also note, that the 4100 carburetor does not actual fit on the COBRA intake by itself.  There would be massive vacuum leaks without some other provisions.  There is a quarter inch spacer used to adapt the carb to intake.  This can be seen in my earlier posted image.

Take care

Cory

[S7MS427]

Kevin,

Just to amplify Cory's response, I believe that the only difference between the manual and automatic versions, other than the dashpot, are the jets.  The booster venturi assemblies appear to be the same between the two.  The flow rate is either 595 or 600 CFM, depending on which source you read.

As for the spacer, Cory is correct, you'll need one or have massive vacuum leaks.  Looking at the underside of the carburetor, you'll see that it is not flat and that the Cobra intake manifold mounting pad does not extend to out to the limits of the Autolite's base.  I think I used a Canton Racing Carburetor Spacer, 85-154, available from Summit Racing.  It is made of phenolic, is 1/4 inch thick, and lists for $35.  The phenolic will also help isolate the carburetor from heat.  Hope this helps.

[Dan Case]

This data from Bob Mannel's book agrees with what we found during the survey done last year with unrestored and new old stock carburetors. The paint color daubs come from the research project. For whatever reason, Ford used the same paint color code daub and location on both the "M" and "MA" assemblies.

C4OZ-9A523-C / MA auxiliary venturi assembluies have gotten very rare. The table in Bob's book shows four (4) each different engineering numbered High Performance 289 specific carburetors using that part. They are very often found robbed and replaced with something else in cores for sale.


There were not many production runs by date for the suffix F carburetor assembly based on what data was collected last year.



The survey was pretty broad including Internet searches reaching back to 2002 and correspondence with people in other countries but some dates could have been missed. If you have an unrestored unit with a tag dated not in the chart and you wish to add to the data, please contact me via email.

As a side bar, the parts used to make up either assembly did not all stay the same over the two Ford model years Ford used them. It is not unusual to see cores and "restored" carburetors for sale with a mix of features and parts not seen in assembly line units. The subject of what versions of what was used when is way too complicated for forum posts.

[Bill Collins]

This is all good advice and I would like to add a warning. With you being unfamiliar with these carburetors and possibly in the market for one, you need to be aware of how to spot a fake example converted from a non Hipo 4100.

There are a couple of telltale modifications to the carb body that are very difficult to convincingly perform. They involve casting nubs on the front passenger side. One is drilled and tapped on the standard 4100 to accommodate mounting the automatic choke assembly. This nub is not drilled on the C6ZF- C/F versions. The other is a smooth plug on the original which may be filled in on a repro.

Careful examination will reveal a witness line around the perimeter of the filled hole and/or roughness of the filled areas. I have both an original and a converted example in my inventory and have attached photos of the affected areas on both so you can see the differences.

Hopefully this will help you avoid a potentially expensive mistake!

[Bill Collins]

Here is a closeup of the filled automatic choke mounting hole that better shows the circular witness line where it was filled in.

[pbf777]

     Excellent tutorial, particularly with the inclusion of photographs!   

     Scott.

[S7MS427]

OK, now that we have definitive evidence, I'll retract my statement that the only difference between manual and automatic are the jets.  The primary booster venturi assembly is different as well.  Good to know, thanks Dan!

A big difference between a non-HiPo and a HiPo carb that I didn't see mentioned is the HiPo carb has a cast in stop for the choke just above the primary throttle shaft.  I've seen people weld in a small rectangular piece of aluminum to simulate that stop, but those are crude at best.

Another tell-tail is the boss for filtered air for the choke is left undrilled.  Filtered air is not needed for a manual choke.

[sg66]

Another casting difference is the distance between the red lines. HiPo carbs have less material to prevent interference with choke hardware.  Some fakes cut it back and some don't. Either would still have witness marks from being filled.

[Dan Case]

[Dan Case]

[68blk500c]

Thank you, Dan, for these closeup pictures of the choke cable bracket differences.  You enabled me to identify the "lazy Z" bracket which I have had for years.  Your knowledge is amazing.