What you have is a 1966 4100 1.08 venturi for a 1966 Ford Galaxie 352 automatic transmission. And this particular carburetor is a "California Emission" carburetor.
To meet the brand new california state emissions for 1966, Ford made special 4100 carburetors for their bigger line of cars (Galaxies, Thunderbirds, Mercury's and the GT fairlane)(These were all the FE powered larger cars from 1966 and were all powered by the FE engines 352, 390, 410, and 428).
These carbs were 480 CFM like the small block 4100's but they had internal modifications which allowed them to flow more to feed the larger FE engines.
Many people today mistakenly buy them (or worse knowingly sell them) as the harder to find and rarer (and more desirable and expensive) "mustang" 1.08 small block carburetors. These same people are very disappointed when these carbs do not perform or cause a myraid of problems when installed on the small block engine since they flow differently. Off-idle stumbles and bogging at the transition from off-idle along with improper or non- functioning of the secondaries are a very common problem associated with this installation.
As a carburetor (like the 4300 smog carburetor that would shortly replace the 4100 after 1966) these california emission carbs did not work as well as the 1.12 venturi carbs for even the FE engines, especially when installed on the 390 and the huge 428.
These are easy to identify, any 1966 carb (with a 6 in the starting position of the part mark) that is a 1.08 venturi (1.08 in the "clock" above the accelerator pump) and has a big car designation (A for galaxie, S for thunderbird, M for Mercury, or O for fairlane) is a california emission carb. Since ford in 1966 NEVER installed a 4 barrel 289 in any of these cars.
The only other odd-ball is the 6P-H which is the factory replacement carb ford used for ALL 4100's from 1966 thru the 70's (in some places you could buy these over the counter till the 90's). This carb is a direct replacement for the 1966 "california emission" GT 390 Fairlane automatic and has the identical specs as the 6O-H (C6OF-H 1.08 venturi california emission carb), but FORD used the 6P-H for ALL replacements 4100's.
I have always been told and figured that if Ford were to pick the most generic carb out of all its 4100's (and there are over 100 of them) this would be it. It came on a mid size car, automatic, and is 480 cfm but will flow to the FE but because it was on the fairlane the flow was reduced. There are literally thousands of these out there and I would venture to say it is the most common 4100 made and that exist today. It unfortunatley is also probably the biggest dog out of all the 4100's in my opinion. A case of trying to please all applications and such it doesn't really do the correct job for any.
Hope that helps,
Bill White
White Automotive
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Thank you for your information. Unfortunately, I just fell under the "many" - I was hoping to use this on my 289 rebuild - mustang. Your information has saved me time, money and most importantly frustration! I appreciate your quick response.
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Can this carb be rebuilt to work on a 289? What makes it different than the other 4100's that it wont work on the 289? Is it a physical property or jets, etc?
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What determines a total carburetors flow is the venturi size(s), the annular boosters, the air bleeds, the discharge slots and the jetting.
Together these work in conjunction to give your carb a balanced flow through-out the complete rpm range and load for your vehicle application and engine size and load requirements.
Along with that is some hidden or obscure parameters such as engine modifications, engine volemetric efficiency, Stoich air conditions (how dense the air is at a given moment), elevation.
So lets take the carburetor parameters only (since tuning to the others could be covered in a several books).
If all those things are set up for a 480CFM flow for a 289 engine with around 170HP (stock 289) in a mustang. Everything is running nice and smooth. Now someone places a 600CFM from a galaxie on this 289, right away you can see the engine that was happy and being well fed is now being STUFFED with fuel, this is OK at high rpm, in fact it is now running harder and further than ever before, but at idle and especially at that critical trasition period when the idle circuit drops off and the cruise takes over it is glutted with fuel.
So to correct this a person was told to change jets, which they do by only a "minuscule" two sizes, now you have changed the way the entire carb processes fuel, EXCEPT at idle. So it still is flowing lots of fuel (Remeber the carb thinks its still feeding a 390 galaxie)at idle, at transition the jets now start to take over, and they now are flowing less fuel but the air bleeds are still suppling the SAME AMOUNT OF AIR for the stock jetting, so your air to fuel ratio now went very lean even though you still have MORE AMOUNT OF THIS air/fuel mixture than your 289 can use. SO you still bog but now you also backfire (thats extreme most times you might hear a burble if your listening for it) from larger amounts of air mixture.
Now you go through the RPM ranges still lots more fuel than you need but its more air enriched and than fuel, till you get to the top end. Now your not running as good as you were but you are also flowing lots more air which now can be a dangerous lean (read burnt valves, piston holes).
The california emission carbs had this very problem when installed on to the 352/390/428 engines.
SO can it be fixed, of course, but FORD in its infinite wisdom does not have any information on Annular booster specs, air bleed specs, discharge specs or rates, they do not even list rates for their autolite jets.
So without that information one would just be guessing (and in the process ruining carbs) by drilling out and experimenting.
In this way the holleys and all their specs are much better for racing since they can be adjusted in ways the Autolites can only be guessed at.
Hope that helps,
Bill White
White Automotive
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I am going to tear into this carb and use it as a learning experience. Do you have information that would give me the original jet size specs? I want to make sure that the jets that are in it are the same that were "suppossed" to be in it.
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HAVE A NICE DAY!!!!