Daze, a couple of things worth checking.  Check the primary throttle shaft for wear - usually on the throttle linkage side.  Just wiggle the throttle lever up and down and side to side.  There should be very little wiggle.  And, check for the secondaries closing smoothly.  They can get gunked up and not close fully.
I have a 1.12 on my 302 and it runs well.  It was a "quadrajet" conversion done by Jon at Pony Carbs probably 15 years ago.  He took the 1.12 carb, and put plastic inserts into the primary venturii to get the carb down to the 380 cfm or so.  It worked really well for about 12 years, then the ignition coil went bad, I got a backfire through the carb, and it melted the venturii inserts.  So, I took them out, cleaned and re-gasketed the carb., and am still running it with no problems.  It is surely not as peppy as the Pony Carb modified carb., but it runs well.
Good Luck.

I would venture to guess the idle circuit could use a blast of cleaner and compressed air and the primary float needle dried out and isn't seating well.

It would be well worth your time to get a Echlin rebuild kit from Napa. The beauty of the 4100 is its simplicity, I actually find it a joy to tear down and reassemble.

Pablo, if I ever get around to turning more venturi reducers ala Pony Carbs I'll pm you.

Thanks to everyone who responded.  there is lots of good info here that I can use.

Pablo wrote:

Check the primary throttle shaft for wear - usually on the throttle linkage side.  Just wiggle the throttle lever up and down and side to side.  There should be very little wiggle.  And, check for the secondaries closing smoothly.  They can get gunked up and not close fully.

Good things to check, however those things were fine, I checked both of them before the carb went on the car.

Pablo wrote:

I have a 1.12 on my 302 and it runs well.  It was a "quadrajet" conversion done by Jon at Pony Carbs probably 15 years ago.  He took the 1.12 carb, and put plastic inserts into the primary venturi to get the carb down to the 380 cfm or so.  It worked really well for about 12 years, then the ignition coil went bad, I got a backfire through the carb, and it melted the venturi inserts. 

I am glad you mentioned the "Spreadbore " technique that poneycarb used.  I found a FAQ from their old website with info on the mod.  I also found several pages where inserts were made using a copper tubing reducer.  The way they did t leave a little something to be desired but I believe I can use their idea and do the same with a little finesse

​

bulletbirdman wrote:

Daze,
Take a look at the power valve I've found these corroded up even in running carbs, off idle to around 2k is where these operate.

Jon Richard wrote:

I would venture to guess the idle circuit could use a blast of cleaner and compressed air and the primary float needle dried out and isn't seating well.

It would be well worth your time to get a Echlin rebuild kit from Napa. The beauty of the 4100 is its simplicity, I actually find it a joy to tear down and reassemble.

​I have ordered a rebuild kit for the carb so I will replace all of that.  thanks for the suggestion.
​

boomyal wrote:

For starters any 1.12 venturi big block 4100 CANNOT be adjusted to work well on a small block. 

​

boomyal wrote:

I will reiterate!  History and experience has shown that big block 1.12  Autolite 4100's cause all manner of intactable problems when used on small blocks

Boom thanks for the input.  You are not the first person I have heard say that , however I get mixed reports.  Others like Pable have had success.  I don't think it is quite a clear cut as a 1.12 4100 won't work on a SB.  There are to many variables, intake, heads, displacement and so on.  In my case its a performance 302 with high flow aluminum intake and heads.  It is also a rebuild so instead of being a 302 its actually a 309.  I will take your info under advisement.  I plan on rebuilding the carb and sleeving the venturi so if it works I will have some info to share but if it doesn't work I will be the first to admit that I should have listened to your experience.  either way should be a fun project and worst case scenario I will have a freshly rebuilt carb to list on eBay  
 

Day, google Mikes carburetors. Good source for parts and info including some videos. I'd contact him for further discussion.

Daze wrote:

I have done a lot of reading and what I have found tells me that if I sleeve the venturi and change the jets I should have a carburetor that is good for any SB however it will be almost perfectly suited for my SB because it is in my Galaxie.  I found it interesting as I was reading that the difference between the 1.08 and the 1.12 carbs has more to do with car size and how the weight of the car loads the engine rather than venturi size.  That is why the big block 1.08 carbs still don't do as well on most small blocks because most small blocks are in small cars.  I could be totally wrong but once I get my Carb rebuilt and setup for my 302 it should be about perfect for my application. at least that is what I am hoping

You're not totally wrong but that's only half the story. The fuel curve is metered through the booster clusters, which are designed for whatever signal strength that is determined by both the venturi size and air velocity.

I think what boomyal is saying is that Ford never published the info needed to identify differences in boosters and without that modifying these becomes a lot of trial and error.

To get it "really right" you'll need to map your fuel curve and be prepared to make changes to things like the idle air bleeds and emulsion tubes- jet changes and power valves won't get you there.

It can be made to work but to really know accurately it's a bit tougher to do than on something designed to be tinkered on.

Looking forward to your follow up.

Jon Richard wrote:

To get it "really right" you'll need to map your fuel curve and be prepared to make changes to things like the idle air bleeds and emulsion tubes- jet changes and power valves won't get you there.

I totally agree with you that there is more to this than jet size and venturi size however I don't have the knowledge base to change more than those two things.  It will be interesting to see if it can be "made to work", and if so how well with the modifications I can make.  

The reality is that setting up a carburetor to function with the best fuel curve and efficiency is no where near a "one size fits all" proposition and more of a "one size fits one" kind of thing.

If you take a carburetor and tune it for a bone stock 289 and get it dialed in to be a perfect mach for that engine, you could put that carb on any 289 that is set up the same way and is bing used for the same type of application and the carburetor should function equally as well on the second engine.  However if you leave it on the first engine and begin making changes, than the perfect tune is going to move away from being perfect as changes are made.  Headers, aluminum intake and heads as well as a change in cam specs when changed from bone stock will basically make that engine totally different from the carburetor's perspective.  I know that some carburetors are less effected by changes, but others are far more sensitive.

I have to wonder if that is why the 4100 has the reputation of being such a fantastic carb when set up correctly but also has so many issues when not correctly matched.  Is it possible that it is less resilient to change?  I compare it to the edelbrock performer.  You can take a 600 CFM edelbrock and put it on a 289, 302, 337, 347, 351W, 351C, 352FE or 390FE (all set up is configurations from stock to performance) and get it to work well with out changing the jets or modifying anything in the carb, yes it would be better with the correct tune but can be made to function well on all those engines right out of the box.  Obviously that is not the case on the autolite 4100 and the more research I have found, the more different versions of this carburetor I have found other than the venturi size.  I figure if Ford used so many different versions of the same carb based on application than that carb must not be as good at dealing with changes to the system.  On the flip side when set up correctly the 4100 is arguably a way better carburetor than a properly tuned edelbrock so I guess the trade of is performance and efficiency for versatility, and I wonder if thats why Ford moved away from the 4100. One size fits many is a whole lot cheeper to mass-produce than one size fits one.
 

Update, I solved 90% of my problems.  I didn't realize the 4100 needs a special base gasket and I had a vacuum leak.  After making the correct gasket I was able to get the car running fairly well, it still has some issues but I am hoping to address them in the rebuild and sleeving.  I will let you know how it goes as things progress.

Daze wrote:

Update, I solved 90% of my problems.  I didn't realize the 4100 needs a special base gasket and I had a vacuum leak.  After making the correct gasket I was able to get the car running fairly well, it still has some issues but I am hoping to address them in the rebuild and sleeving.  I will let you know how it goes as things progress.

What intake manifold are you running it on?  If it was an Edelbrock, Holley or Weiend, it needs an adapter plate.

I made an update to this project in a new thread.  Figured I would mention it so those of you who are following this thread would know about the new one.
 

You had counseled me once before to turn the spacer upside-down to avoid a vacuum leak in this thread-

http://fyi.boardhost.com/viewtopic_mobile.php

But be aware those holes taper to a larger diameter at the bottom so as to slow the velocity to help prevent the fuel from falling out of suspension,  so inverting the spacer will do the opposite and speed it up before it enters the intake plenum.

The last few base gaskets I got out of rebuild kits had the holes cut so large that there was barely enough coverage around the edges of the throttle bores, leading me to believe these are meant for between the spacer and manifold and not spacer to carburetor.

http://fyi.boardhost.com/viewtopic_mobile.php?id=1220

Hopefully the link works this time.

Yes I remember reading a post of yours regarding the differences between the spacers with regard to how the crank case gasses are routed differently.