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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