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September 28 2007 at 12:43 AM
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Bill White  (no login)
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Response to Carburetor calibration/specs

Each and every (and theres about 120 +/- variations of 4100's) carb will have its own or share a set of specifications for several carburetors based upon whether its a 1.08 vs 1.12, differing boosters, and differing air bleeds and idle discharge slots.

Ford engineering has determined the variations of the 4100 based on what the expectation of the carb and the application, They are the ones who also established the settings for all the carburetors. Those various settings have been published (or republished) in various places.

The original place those settings were found is in the original equipment specification books, small books that all ford approved (dealership) mechanics got every year from the dealership. These same settings were also found in the original equipment shop manuals.

All good repair kits will have a copy of the specifications in order to bench set that particular carburetor. One of the problem with cheaper kits is they do not contain this or contain faulty or incomplete specs.

You definetly do not want to be "interchanging" parts such as venturis and willy nilly replacing jetting since these are two (of the many) of the fastest ways to disrupt the carburetor settings. Same with using specifications that are intended for another car or a hodge podge of specifications.
(For example using a 66 mustang specs because you think that will give you more pep for your 61 galaxie, the 61 galaxie carburetor is intended to work perfectly with those 61 galaxie specs, by changing to the 66 mustang specs (different variety of the same carb) will cause that 61 carb to act differently and throw it out of balance.)

The reason is the WHOLE carburetor works in conjuction with itself, that particular carburetor has unique idle disharge ports, unique air bleeds, which work with a given set of boosters and a given set of jetting and the various settings, any of those are different and the whole ratio of air to fuel changes and the whole timing of the air/fuel ratio can be disrupted.

Think of it as a cherry pie, when baking if you add less sugar, you still have a cherry pie when your done but it will taste completely different, how about more baking powder or more butter...... Get the idea.......

Now some changes are minor and will not disrupt the carb as much, like for example going 1 or 2 jet sizes bigger. Adding two jet sizes will disrupt the flow but minor enough that it just changes the timing of the air/fuel mixture. More than 2 ets sizes will throw if off significanlty more, maybe not enough for you to notice but I can assure you 3 jets sizes (or more) will show on on a dyno and an air fuel meter. That is why you always hear me talking about NEVER going more than 2 jet sizes. It is my believe (after testing on the above machines) that 3 (or more) jet sizes will throw your carb out of Stoic. (fancy way of saying more than the 12.5-14.5:1 air fuel ratio that the carbs were originally set up for)

The other problem with mixing and matching is if there was some sort of table or data that showed ALL OF THE MANY VARIATIONS AND WHAT THOSE EXACT VARIATIONS for each carburetor and how they INTER-ACTED with each other, then one could logically start switching and swapping pieces for what ever idea they were looking for.

BUT unfortunatley no such information exists from either AUTOLITE nor from FORD.
Trust me I have spent 15 years looking for this information as its the HOLY GRAIL of carburetor info.
I have talked to several mechanics/people who claim to have this info and after talking to them I am certian they have no information that was ever published from either FORD or AUTOLITE. Some of them have been outright frauds or mistaken information.
I have talked to 2 mechanics who I am certain have in their possesion some of this information that they have inquired from their own independent research. How much of the data and how accurate it is remains to be seen. And whether these two can fully use that information and how it applies as each variant acts upon the other also remains to be seen.
How complicated can it be, Just looking at the venturi annular booster for the 2100/4100 it can have over 14 differing measurements for each set of boosters. How does any one of those 14 differing items effect how that booster flows??? And what changes need to be done when any one of those 14 items change???
Remember I am talking scientific analysis and accurate test results rather than swapping parts and getting lucky.

When I was unable to find this type of data, That is when I started to research to create my own, (I had both the time and proper equipment to do this at that time) but the project became UNOBTAINABLE with little to show.

Hope that helps and was what you were looking for.

Bottom line, either get the correct carburetor for your application, or when not possible (like swapping) obtain a carburetor that MOST closely matches your application (with the 2100/4100 that is not all that difficult). Then rebuild it to the CARBURETOR NUMBER/Application that it was originally intended for.

I gave the example of my partners race car, all of those carbs that we use are C8TE-A or B carbs, or 1968 ford truck carbs with a 352-390. Basically the truck is very close to the weight/style of our race cars (heavy front ends/light rear ends and about 3500lbs), and the engines are of like cubic inches (351 vs 352/390) and although the 352/390 FE could use more CFM than our small block 351 our race engine is revving more (lot more) and has more volumetric efficiency than a stock 351.
I still rebuild and use the 1968 ford truck stock specifications for these carbs and we are presently using 2 jets sizes larger than stock. (like I said before we were only 1 size larger before we installed a MUCH LARGER CAM to run on a larger track as we needed more duration on the bigger track). The cam we are running is a full out race cam that WOULD NEVER SEE THE STREET.

Bill White
White Automotive

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  1. Great info - 74ford on Sep 28, 2007, 9:00 AM
    1. Thats why....... - Bill White on Sep 28, 2007, 12:57 PM
      1. When can I get mine? - Paul on Oct 1, 2007, 4:59 PM
        1. correct cam numbers - Paul Tessier on Oct 2, 2007, 10:20 PM
          1. hmm...summit 4010 boosters...plus other hop up tricks - Anonymous on Feb 23, 2009, 7:38 PM
  2. well thought out - Dave H on Apr 30, 2012, 11:33 PM
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