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7/09/2016 6:37 PM  #1


Modifying an Autolite 4100 1.12 to work on a small block 302

A few weeks back I made a post needing trouble shooting help with an autolite 1.12 4100 that I was trying to make work on the 302 in my 62 Galaxie.  After much discussion and trouble shooting I found that it was a vacuum leak and was able to get it working OK but not as good as the Edelbrock I had removed to install the Autolite.  Obviously the 1.12 carb that I have was setup for a big block and my 302 even though performance is no big block.  Throughout the discussion on that thread I was given a couple pieces of key information, first Pony Carbs use to sell plastic inserts to convert the 1.12 carb into what they call a "spread-bore" carb.  They worked simply by sizing down the venturi.   Further research on the net provided info where a guy used a plumbing adapter to modify his 4100.  his attempt while functional was a little crude for my tastes.  The second piece of info I receive from my previous thread was a link to a carb forum that after a little searching provided tons of info on this "spread -bore" mod as well as some suggestions as to jet size.

My plan after doing the research was to rebuild the Carburetor, replace the jets, and make my own sleeves.  The rebuild has begun. I have a rebuild kit, and have fully disassembled the carb.  The jest that came in the carb were 55/62 and I need 49/55 so I will order some 49 jets to replace the front ones and move the original front jets to the rear.  The sleeves were the next thing to tackle.  I made a set out of some coper pipe.  I cut it to length and faced both ends on my lathe.  I then flanged the top of the sleeves and cut a notch in the bottom of the sleeves.  Once I had the rough shape I had to slightly work the outside of sleeves with sandpaper to get a nice fit in the bore of the carb.  The final result is a sleeve that can be pressed in tightly by hand.



as you can see from the following pix the fit is nice and I am hoping that that will work as well in reality as they do in theory.



If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
 

7/09/2016 6:58 PM  #2


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Hey Daze, The pictures aren't there.


John  -- 67 Mustang Coupe 390 5 speed
 

7/09/2016 7:12 PM  #3


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Bolted to Floor wrote:

Hey Daze, The pictures aren't there.

Might want to try a refresh or somthing on your computer.  The pix are coming up on my computer and I also pulled this thread up on my phone and the pix are there.


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/09/2016 7:30 PM  #4


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Nice work!

 

7/09/2016 7:45 PM  #5


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Pics are working on mine. Very cool Daze, were you able to get a measurement on the final venture?


If this forum can't fix it, it isn't broke.
 

7/09/2016 8:29 PM  #6


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

wsinsle wrote:

were you able to get a measurement on the final venture?

I never thought to measure the new bore.  When I was measuring to find a suitable tube I was only worried about the OD of the pipe so that it would fit properly.  I figured what ever fit would be what I had to use and as long as it was at least 1" I would be good to go.

I went out to the garage and put a bore gage in the sleeves and they came in at 1.05".  I know its a little less than the 1.08" but I don't really see the need to try an enlarge the bore of the sleeves.  The smaller bore should give better throttle response and if the engine needs more air the vacuum secondaries should come open to compensate.
 


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/09/2016 10:13 PM  #7


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Are you sure that you do not want to feather the leading edge of those inserts?  Otherwise, they look great.

 

7/09/2016 10:22 PM  #8


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Thanks!!  its hard to tell in the pix but the leading edge is actually feathered.  Its angled to match the carb and then the inside lip is rounded off for a smoother transition.  I polished up the copper after I shaped it and the flash off the polish is what is making it look more like a normal lip.


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/10/2016 9:35 AM  #9


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Daze wrote:

Thanks!!  its hard to tell in the pix but the leading edge is actually feathered.  Its angled to match the carb and then the inside lip is rounded off for a smoother transition.  I polished up the copper after I shaped it and the flash off the polish is what is making it look more like a normal lip.

Good to know.  They sure beat using plastic.  Will you use any locktite on them once you make a final determination as to their suitability?  Being an AutoLite fan, I'll be anxious to see the outcome.  Are you going to be able to make any comparisons of the boosters?
 

 

7/10/2016 11:47 AM  #10


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

http://www.ebay.com/itm/1965-Ford-Mustang-Autolite-4100-Carburetor-C5OF-J-/172268694552?hash=item281c03ac18:g:eDQAAOSwAPlXgUD1&vxp=mtr   And he HAS to have a core!

Perfect those inserts and you might just make a small fortune selling them!  Maybe Im getting old, but I remember going to a swap meet back in the 90's and a guy had a whole pile of 4100's for 5 to 10 dollars apiece.   Nobody wanted them.  Pony carbs did for Autolites what Barrett Jackson did for classic cars.  

Last edited by Greg B (7/10/2016 11:55 AM)


If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
 

7/10/2016 1:04 PM  #11


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Now that is proud, isn't it?  However, and I am surprised he does not make a point of this, that C5OJ is a 1:12 venturi, manual choke, originally installed on '65 Mustang and Fairlane HiPo's.  It would be pretty rare.

 

7/10/2016 8:10 PM  #12


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

The Pony Carbs reducers measure 1.00" I.D. and appear to be made of nylon-





My boosters are stamped KA, but bare in mind that designation was used on a 1.12, a 1.08, and an early 2100 with 1.01 venturi and I haven't had time to measure everything to verify what Jon at Pony put in this carb. I know that emulsion tubes and emulsion wells do vary in size for the autolite family of carbs and that plays a big role in how and when the mixture is metered and delivered.

 

7/10/2016 8:45 PM  #13


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Nice fab work. Can't wait to see how it runs.
I really like your willingness to tear into something and try out a theory.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

7/10/2016 11:11 PM  #14


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Greg B wrote:

Perfect those inserts and you might just make a small fortune selling them!  

That is a long ways out but is somthing I thought of when I first started this project.  if I can make it simple enough to work well in most applications than its a go.  As I was flaring the pipe I came up with a custom die design so that I can make them all the same.  

boomyal wrote:

Will you use any locktite on them once you make a final determination as to their suitability?  Being an AutoLite fan, I'll be anxious to see the outcome.  Are you going to be able to make any comparisons of the boosters?
 

I really dont think Locktite will be needed. With the lip on the top and the vent tube in the bore there is no way for the part to drop down into the bore, and with them being a slight press fit I don't expect them to work up and out.  When I installed them I was able to press them in by hand but once fully seated I had to use a brass punch and small hammer to get them back out.  As to the boosters I have nothing to compare them too so I really can't say what the differences are.

Jon Richard, Thanks for posting the pix!!!  I searched the net hoping to find pictures (why reinvent the wheel) but never could find anything.​

MS wrote:

Nice fab work. Can't wait to see how it runs.
I really like your willingness to tear into something and try out a theory.

Thanks!!  for me thats the fun part.  in fact often times it takes me a long time to fully finish a project because once I have all the bugs worked out of something its not as fun.  I like the problem solving and the challenge of creating something from nothing or making a part work well in a way that it was never intended to work. 

 


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/23/2016 10:00 AM  #15


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

After several different changes to my die and a couple of different adapter designs I now have what I think is going to be the best adapter I can make with what I have, spreadbore adapter 2.0.  These insets have more of a flair to them and they match the contours of the carb body better.  They are also shorter which means it doesn't need to be notched to clear the tube, and the shorter sleeve has less change to the shape of the original carb bore.



The sleve on the right inside the carb has been worked to have a smooth transition but the one on the left still needs to be  feathered.


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/23/2016 11:08 AM  #16


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Amazing detail Daze. I can't wait to see how it works out for you.

 

7/24/2016 12:07 AM  #17


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Your thread got me excited about these carbs again and I've bought two more rare/ unique 4100's since you've posted and have done some more measuring- you bad influence!

I have a few Edsel 4100's from '58 that have 1.06" primary venturi size, thats the closest in size Ford produced to what you have. I could measure the booster orifices with precision for comparison should you decide to really play with the fuel curve.

That's me trying to influence you ;)

 

7/24/2016 9:02 AM  #18


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Nice very nice.


I made enough money to buy Miami, but pissed it away so fast
 

7/24/2016 10:49 AM  #19


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Daze, is your 'die' such that you would be able to turn those reducers out in mass?

 

7/24/2016 1:15 PM  #20


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

boomyal wrote:

Daze, is your 'die' such that you would be able to turn those reducers out in mass?

 
Yes that is the plan, but only if I can meet the following criteria: first it has to work and work well, I won't sell them if it only sort of works. Second I need to be able to make them quickly and easily and still be a quality piece so that I can keep the costs down. I like all my products to be as affordable as possible.


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/24/2016 4:36 PM  #21


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Hope you can make it all work.

 

7/26/2016 8:09 AM  #22


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Greg B wrote:

http://www.ebay.com/itm/1965-Ford-Mustang-Autolite-4100-Carburetor-C5OF-J-/172268694552?hash=item281c03ac18:g:eDQAAOSwAPlXgUD1&vxp=mtr   And he HAS to have a core!

Perfect those inserts and you might just make a small fortune selling them!  Maybe Im getting old, but I remember going to a swap meet back in the 90's and a guy had a whole pile of 4100's for 5 to 10 dollars apiece.   Nobody wanted them.  Pony carbs did for Autolites what Barrett Jackson did for classic cars.  

Question from the auction:

Q: I'm interested in the C5OF-J carb but think there is a mistake in the price. I presume it was meant to be listed at $999.95 rather than almost $10,000. If the price is $999.95 please let me know as I would like to buy the carb. Thanks

A: Hi, Thank you for Your Question, Their is Honestly No Mistake, the Cost of the Carburetor is indeed $9,999.95. I am Open to Offers, however as of Now, the Price you see is the Price We are Selling this Carburetor for. Dan P.s. We are Always getting in Ford Carburetors, is their any Other Carburetor you were Looking for?


Another eBay seller on crack!
 


Dan      Presently own: 1965 Coupe, 200cid, 3spd.
 

7/26/2016 1:04 PM  #23


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

At least the shipping is free....

 

7/29/2016 6:00 PM  #24


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

Jon Richard wrote:

Your thread got me excited about these carbs again and I've bought two more rare/ unique 4100's since you've posted and have done some more measuring- you bad influence!

I have a few Edsel 4100's from '58 that have 1.06" primary venturi size, thats the closest in size Ford produced to what you have. I could measure the booster orifices with precision for comparison should you decide to really play with the fuel curve.

That's me trying to influence you ;)

I like being a bad influence.  this project is going along all be it slow.  I got some size 48 jets to put in the front and I will move the original 55 front jets to the back.  I have the rebuild kit and the "bugs" worked out of my inserts.  now all I need to do is get all the parts cleaned up, an put it all back together. 

As to messing with the boosters I think I have a plan there as well.  The openings for the primary boosters are small but the openings for the secondary boosters are huge, they are labeled B and C with B being the bigger one from the secondaries and C being the smaller one from the primaries.  I also have two other autolite carbs that I collected over the years, both are 2 barrel.  One came from a 69 pickup with a 360 in it and the other was the carb that came on the 352 that was in my galaxie when I got it.  I have pulled the boosters from both of those carbs and one is stamped AA and the other is stamped D.  Both have smaller openings than the the B booster from the 4 barrel carb's secondaries but are slightly larger than the C booster.  What I think I will do is run the 4100 as it came from the factory (with the exception of smaller jets) after I finish the rebuild.  I will then install the inserts and see what kind of a difference they make in performance.  After that I will swap out the secondary booster for one of the smaller ones and see if the carb functions even better.

funny thing is this is all more of an exercise in knowledge and now possibly a new DazeCars product.  I have always preferred Edelbrock carbs over Holley's because even though they produce slightly less power I like their  "one size fits many" ability and the fact that they are relatively maintenance free.  I started this project hearing of the nearly mythical properties of the the 4100 so I wanted to try it and see if it was as good as they say.  However after doing a bunch of research I have learned that basically the autolite 4100 is functionally similar to a Holley so when its all said and done I will probably put the Edelbrock back on after I finish the project.


If it isn't broken...modify it anyway! http://www.DazeCars.com https://galaxieforum.boardhost.com
     Thread Starter
 

7/29/2016 6:49 PM  #25


Re: Modifying an Autolite 4100 1.12 to work on a small block 302

When you say the size of the openings are you referring to the physical dimension of the booster venturi itself where the annular fuel discharge holes are housed?

I was talking about all the tiny holes like the idle jets, idle air bleeds, and holes in the emulsion tubes. Those little buggers are what make the 4100 such a black art to tune.

You also have to pay attention to the I.D. of the main wells and the O.D. of the emulsion tubes meant for your particular carb because they are different in the Autolite family, and will have a heavy influence on how fuel is metered.

It's crazy because it really is as simple as having the right size passages,  the hard part is figuring that out. I really don't subscribe to the idea that 4100's are harder to tune than Holleys because resizing holes is the easy part.

 

Board footera


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