Autolite 4100 Tips
Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
I'm having issues with mine idleing to high.
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Anybody got any ideas on how to get her to idle down a little bit more?
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Anybody got any ideas on how to get her to idle down a little bit more?
Lead Driver
Joined: Feb 2000
Posts: 5,374
Likes: 46
From: Palm Bay, Florida
My Brother-In-Law threw a 4100Hipo carb (from a '65 289 Hipo/manual choke) away YEARS ago, I had a clone made by Pony Carbs that is now out of business.
Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
I will check what boosters i have in the carb, i built one carb out of two, so i may of mixed the wrong boosters in there.
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,193
Likes: 385
From: Near Los Angeles
I'm running it. I ran initially with 47 primaries and 67 jets in the secondaries. Wow, it really got up and went on a run, but back at the garage I noticed it smoking a bit at idle, and when I punched it with my hand I got a puff of black smoke. Rich. So, I dropped all the way to 44's, and now it is hesitating. It's a lean hesitation off idle. Tomorrow I'll bump the jets up to 46 in the primaries and see how that works. I also switched to 50's in the secondaries.
Something I noticed: The shot from the acc pump comes out of the boosters as a spray. With my Quadrajet it is a solid stream, like a mouse peeing. Maybe that is one reason for great mpg with these carbs: spray will atomize easier than a stream.
Note: These carbs are finicky about the base gasket. I eventually found that a Felpro 60046 works great. I had hoped to use a 1/4" thick insulating gasket, since with the 300 I6 my intake sits right above the header and it soon starts to roast, but I couldn't get it to run correctly with one. Most likely I could not find the correct gasket, since I noted that when I removed the oem carb it was sitting atop one such gasket.
Something I noticed: The shot from the acc pump comes out of the boosters as a spray. With my Quadrajet it is a solid stream, like a mouse peeing. Maybe that is one reason for great mpg with these carbs: spray will atomize easier than a stream.
Note: These carbs are finicky about the base gasket. I eventually found that a Felpro 60046 works great. I had hoped to use a 1/4" thick insulating gasket, since with the 300 I6 my intake sits right above the header and it soon starts to roast, but I couldn't get it to run correctly with one. Most likely I could not find the correct gasket, since I noted that when I removed the oem carb it was sitting atop one such gasket.
Hotshot
Joined: Jun 2010
Posts: 11,424
Likes: 2
From: Big Sky Country
I'm having issues with mine idleing to high.
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Where they ever removed from the throttle shaft? After 40+ years they tend to wear into their throttle bores and get tempermental about being moved to a new one. Hold the carb up to a light and see if the throttle blade is slightly misadjusted one way or the other and getting hung up in the bore.
Anybody got any ideas on how to get her to idle down a little bit more?
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Where they ever removed from the throttle shaft? After 40+ years they tend to wear into their throttle bores and get tempermental about being moved to a new one. Hold the carb up to a light and see if the throttle blade is slightly misadjusted one way or the other and getting hung up in the bore.
Anybody got any ideas on how to get her to idle down a little bit more?
Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
Yeah I tore the carb completely down to rebuild, but I marked the butterfly's before I did, I did notice when I installed the butterfly's they were hanging up then to, but I readjusted them to where they would completely close or so I thought.
Thanks for the info on the boosters, I'm not sure what boosters are in there, I just marked which one was primary and secondary on both carbs, so I may of mixed the boosters upon installing them.
Also is it wise to run a fpr? I ask because mine is seeping a little gas on the secondary bowl and I've tightened the screws as tight as they will go. And I was wondering if the stock fuel pump is over pressuring the carb?.
Thanks for the info on the boosters, I'm not sure what boosters are in there, I just marked which one was primary and secondary on both carbs, so I may of mixed the boosters upon installing them.
Also is it wise to run a fpr? I ask because mine is seeping a little gas on the secondary bowl and I've tightened the screws as tight as they will go. And I was wondering if the stock fuel pump is over pressuring the carb?.
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,193
Likes: 385
From: Near Los Angeles
The boosters are calibrated for the carb, hence the list number, and as such can throw off your base tuning in a hurry once you start swapping them. I have seen a few high idle conditions corrected by just swapping in the correct boosters for the carb. I would swap the boosters back in and set the carb up to whatever vehicle it is listed for and then tune from there.
I will say that I've noticed one difference on the big block 1.08's, the 480 cfm Ford put large engines. On these carbs Ford drilled an air bleed through each barrel and into the top of the fuel emulsion tube housing, just like Quadrajets have. This allows the fuel to flow much faster, in greater volume than the 1.08's without the air bleed.
(An air bleed is nothing more than a hole that allows air in to increase flow. Imagine you're pouring milk from a plastic jug. It chugs as it tries to escape the narrow opening. But, if you take a pen and poke a hole into the milk jug and allow air in, it pours without chugging. That is an air bleed.)
Regarding the sticking butterflies:The leading edge of each butterfly is beveled. Opposite edges on the same butterfly are beveled in different directions. Make sure you have the bevels working to seal the barrels.
If they are in correctly, and still binding, strip down the top of the carb, empty it, remove floats and boosters, and place it upside down on a 2X4 block. If you used loctite on the butterfly screws, heat them with a propane torch and loosen them a couple of turns. Only heat enough to make the loctite to let go. Once all four screws are loosened, work the shaft back and forth. Lube the shaft. When they are sitting well, both seated properly, just snug the screws a bit, and check how they open. Loosen and move as needed until they don't stick. Good luck
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,193
Likes: 385
From: Near Los Angeles
How sweet it is!
I've been driving with a Quadrajet on for a long time. Right away I could hear and feel a difference. The adapter I used funneled the secondaries of the QJ down to a Holley configuration. The mix entered my intake at about a 45* angle. I don't know if that contributed to the quality of the idle, but I am amazed how smooth the 4100 idles.
Surprisingly, the throttle/acceleration is more responsive too. I thought the QJ, with its tiny primaries, would send a tremendous signal, but the 4100 has it beat.
I did mod the mix orifices, enlarging them a few 1/1000 ths. Once I did that I got a rough idle even with new screws. So ... I noticed that QJ screws were the same thread, and longer. I tried them and ... bingo!
I now have a spare 4100. Ugh.
Surprisingly, the throttle/acceleration is more responsive too. I thought the QJ, with its tiny primaries, would send a tremendous signal, but the 4100 has it beat.
I did mod the mix orifices, enlarging them a few 1/1000 ths. Once I did that I got a rough idle even with new screws. So ... I noticed that QJ screws were the same thread, and longer. I tried them and ... bingo!
I now have a spare 4100. Ugh.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,193
Likes: 385
From: Near Los Angeles
I wanted to stress that I had to use a fuel psi regulator for this carb. I only had 4 psi from the oe pump, but it was oozing/fizzing past the needle seat, no matter which type I tried. I dialed the regulator ( a mr. Gasket with a dial) down to .5, and it works fine. Flow, not psi.
I also had to file flat the acc pump cover to get it to seal. The oem coolant circulating spacer was too warped to use.
I also had to file flat the acc pump cover to get it to seal. The oem coolant circulating spacer was too warped to use.
Hotshot
Joined: Jun 2010
Posts: 11,424
Likes: 2
From: Big Sky Country
I believe all the carb bodies are the same except the hipo's. It seems all the fuel passages are the same. The differences all in the boosters, emulsion restrictions regulate the amount of fuel that flows. Each booster has different air bleeds too. That would make since with Ford too: at the factory they could use the same core on many engines, just change the boosters to fit a specific car.
I will say that I've noticed one difference on the big block 1.08's, the 480 cfm Ford put large engines. On these carbs Ford drilled an air bleed through each barrel and into the top of the fuel emulsion tube housing, just like Quadrajets have. This allows the fuel to flow much faster, in greater volume than the 1.08's without the air bleed.
(An air bleed is nothing more than a hole that allows air in to increase flow. Imagine you're pouring milk from a plastic jug. It chugs as it tries to escape the narrow opening. But, if you take a pen and poke a hole into the milk jug and allow air in, it pours without chugging. That is an air bleed.)
I will say that I've noticed one difference on the big block 1.08's, the 480 cfm Ford put large engines. On these carbs Ford drilled an air bleed through each barrel and into the top of the fuel emulsion tube housing, just like Quadrajets have. This allows the fuel to flow much faster, in greater volume than the 1.08's without the air bleed.
(An air bleed is nothing more than a hole that allows air in to increase flow. Imagine you're pouring milk from a plastic jug. It chugs as it tries to escape the narrow opening. But, if you take a pen and poke a hole into the milk jug and allow air in, it pours without chugging. That is an air bleed.)
The worse part is there is no documentation (that I have ever found) describing all these variables and how they interact, So to put the boosters from a smaller 1.08 carb into a larger 1.12 carb is simply a crap shoot where you are hoping and praying for a desired result but really have no clue as to what is going to happen or the results that will occur.
Now if you had a bunch of time and expensive testing equipment, one could probably start rigging together carburetors and maybe stumble upon a good combination, but remember there are over 100 VERSIONS of the 4100, probably at least 30 or more versions of boosters (especially counting 2100 boosters as well). So which 1.08 booster do you choose, and which 1.12 body do you choose, will any booster work with other bodies? Im convinced this is what some of the major carb rebuilders do, mix and match pieces to get the finished product out the door and of course that is also why some rebuilds are crap and run like crap and you can never get them tuned. Bottom line is since there is no documentation of all the interacting pieces, putting anything together is a crap shoot.
I am constantly running into carbs with mixed innards, which is really unfortunate. These carbs will sit in my parts tub since there is no way to guarantee any accuracy of being tunable or runable in my experience.
I believe if there were only a handful of boosters and one or two main bodes you would not see the degree of list numbers that you do. My intent is not to start an argument but only offer my take on the 4100 that is shared by a few others
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,193
Likes: 385
From: Near Los Angeles
Great analogy on the air bleeds but I don't believe the calibration of these carbs are all in the boosters as the boosters work in conjunction with all of the variables these carburetors have, namely jetting, float levels, idle discharge passages and slots, transfer ports and air bleeds. Even if the boosters have the same number they may be calibrated differently. Basically they are calibrated for each carb and each carb core can have differently sized restrictors and transition slots/holes which affect the main jetting.
The worse part is there is no documentation (that I have ever found) describing all these variables and how they interact, So to put the boosters from a smaller 1.08 carb into a larger 1.12 carb is simply a crap shoot where you are hoping and praying for a desired result but really have no clue as to what is going to happen or the results that will occur.
Now if you had a bunch of time and expensive testing equipment, one could probably start rigging together carburetors and maybe stumble upon a good combination, but remember there are over 100 VERSIONS of the 4100, probably at least 30 or more versions of boosters (especially counting 2100 boosters as well). So which 1.08 booster do you choose, and which 1.12 body do you choose, will any booster work with other bodies? Im convinced this is what some of the major carb rebuilders do, mix and match pieces to get the finished product out the door and of course that is also why some rebuilds are crap and run like crap and you can never get them tuned. Bottom line is since there is no documentation of all the interacting pieces, putting anything together is a crap shoot.
I am constantly running into carbs with mixed innards, which is really unfortunate. These carbs will sit in my parts tub since there is no way to guarantee any accuacy of being tunable or runable in my experience.
I believe if there were only a handful of boosters and one or two main bodes you would not see the degree of list numbers that you do. My intent is not to start an argument but only offer my take on the 4100 that is shared by a few others
The worse part is there is no documentation (that I have ever found) describing all these variables and how they interact, So to put the boosters from a smaller 1.08 carb into a larger 1.12 carb is simply a crap shoot where you are hoping and praying for a desired result but really have no clue as to what is going to happen or the results that will occur.
Now if you had a bunch of time and expensive testing equipment, one could probably start rigging together carburetors and maybe stumble upon a good combination, but remember there are over 100 VERSIONS of the 4100, probably at least 30 or more versions of boosters (especially counting 2100 boosters as well). So which 1.08 booster do you choose, and which 1.12 body do you choose, will any booster work with other bodies? Im convinced this is what some of the major carb rebuilders do, mix and match pieces to get the finished product out the door and of course that is also why some rebuilds are crap and run like crap and you can never get them tuned. Bottom line is since there is no documentation of all the interacting pieces, putting anything together is a crap shoot.
I am constantly running into carbs with mixed innards, which is really unfortunate. These carbs will sit in my parts tub since there is no way to guarantee any accuacy of being tunable or runable in my experience.
I believe if there were only a handful of boosters and one or two main bodes you would not see the degree of list numbers that you do. My intent is not to start an argument but only offer my take on the 4100 that is shared by a few others
It is a shame that Jon of Pony Carbs passed. After a life time dealing with the 4100, I'll wager that somewhere he had charts and reference numbers for all the variations of the 4100.
What I learned: Following the same train of thought as the discourse above, I leaned that with all the variations of the 4100, with all the parts being swapped, and because there is a lack of documentation allowing an owner/builder to return any 4100 to oe specs, and because they have been mixed and matched for 40+ years, if I were looking to buy a carb today, I would spend some more and purchase a new Holley or Summit carb. I like the Summit carb, but thought the minimum size 600 cfm might prove too large for my 300 I6.
Not to kick the hornet's nest, but I read that the Summit carb is a remake of the 4100, using a double fuel inlet where the 4100 uses a single, and that the boosters off the Summit Carb will interchange with the 4100.
With the 47s in the primaries it was running rich. I dropped way down to 44's and got a lean hesitation off idle. I installed 46's and the problem was solved.
Elder User
Joined: Mar 2004
Posts: 747
Likes: 0
From: Klamath Falls OR
What I have is two 4100's. The one I bought on ebay was so bad that I needed another just to make one good carb. Both are the big block 480 cfm 1.08 venturi size.
Boosters: The C6A F had what looked like performance boosters, judging by the size of the air bleeds and the diameter of the end of the emulsifier tube, if that is what you call the tubes that stick down into the carb body from the boosters. The primary was DK, and the secondary was F.
Since this carb came off a 390, I thought it too much flow for my application. So, the C6SC I took apart had a TD primary booster and an FT secondary. The restrictions in the end of the tubes were much smaller, like those found on a 289 4100, so I thought they were be better suited for my engine. I swapped them over to this carb, the C6AF.
I've noted that it is also difficult to find a base gasket for the 4100. I don't like the open plenum gaskets supplied by most kits. I noted the oem gasket on the Tbird from which I removed the C6SC was 1/4" thick, tapered from end to end, with a pcv inlet in the primary side. It also had each primary bore separated, and the secondaries joined, just like Felpro 60046. As an insulating 1/4" think gasket between intake and spacer I'll use Mr.G. 758.
I'll see where that will get me.
I have redone the carb once more, blowing out the boosters and all passages. Hopefully it will idle this time around.
Boosters: The C6A F had what looked like performance boosters, judging by the size of the air bleeds and the diameter of the end of the emulsifier tube, if that is what you call the tubes that stick down into the carb body from the boosters. The primary was DK, and the secondary was F.
Since this carb came off a 390, I thought it too much flow for my application. So, the C6SC I took apart had a TD primary booster and an FT secondary. The restrictions in the end of the tubes were much smaller, like those found on a 289 4100, so I thought they were be better suited for my engine. I swapped them over to this carb, the C6AF.
I've noted that it is also difficult to find a base gasket for the 4100. I don't like the open plenum gaskets supplied by most kits. I noted the oem gasket on the Tbird from which I removed the C6SC was 1/4" thick, tapered from end to end, with a pcv inlet in the primary side. It also had each primary bore separated, and the secondaries joined, just like Felpro 60046. As an insulating 1/4" think gasket between intake and spacer I'll use Mr.G. 758.
I'll see where that will get me.
I have redone the carb once more, blowing out the boosters and all passages. Hopefully it will idle this time around.
First off C6AF-? C6AF-AA ? Whats the last letter or 2??? Same with your C6SC-? what!? You wont know what boosters are suppose to be in there. They are all different from one another. You can guess all you want. But it doesnt mean its right! You really dont know what you have is all correct. Give me the last letter or 2 (some came with 2 letters after the dash). I can tell ya what is suppose to be in there from the factory and what it came off of too.
I have the factory books for that stuff. I rebuild carbs for others and make them correct. Thats part of my Business LOL
Elder User
Joined: Mar 2004
Posts: 747
Likes: 0
From: Klamath Falls OR
What I learned: Following the same train of thought as the discourse above, I leaned that with all the variations of the 4100, with all the parts being swapped, and because there is a lack of documentation allowing an owner/builder to return any 4100 to oe specs, and because they have been mixed and matched for 40+ years, if I were looking to buy a carb today, I would spend some more and purchase a new Holley or Summit carb. I like the Summit carb, but thought the minimum size 600 cfm might prove too large for my 300 I6.
.
.
Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
Your opinion could very well be fact. I leaned toward my guess/opinion because the manufacturer always seeks 'one to fit all' with the least amount of machine work possible to make that happen. You may very well be right.
It is a shame that Jon of Pony Carbs passed. After a life time dealing with the 4100, I'll wager that somewhere he had charts and reference numbers for all the variations of the 4100.
What I learned: Following the same train of thought as the discourse above, I leaned that with all the variations of the 4100, with all the parts being swapped, and because there is a lack of documentation allowing an owner/builder to return any 4100 to oe specs, and because they have been mixed and matched for 40+ years, if I were looking to buy a carb today, I would spend some more and purchase a new Holley or Summit carb. I like the Summit carb, but thought the minimum size 600 cfm might prove too large for my 300 I6.
Not to kick the hornet's nest, but I read that the Summit carb is a remake of the 4100, using a double fuel inlet where the 4100 uses a single, and that the boosters off the Summit Carb will interchange with the 4100.
With the 47s in the primaries it was running rich. I dropped way down to 44's and got a lean hesitation off idle. I installed 46's and the problem was solved.
It is a shame that Jon of Pony Carbs passed. After a life time dealing with the 4100, I'll wager that somewhere he had charts and reference numbers for all the variations of the 4100.
What I learned: Following the same train of thought as the discourse above, I leaned that with all the variations of the 4100, with all the parts being swapped, and because there is a lack of documentation allowing an owner/builder to return any 4100 to oe specs, and because they have been mixed and matched for 40+ years, if I were looking to buy a carb today, I would spend some more and purchase a new Holley or Summit carb. I like the Summit carb, but thought the minimum size 600 cfm might prove too large for my 300 I6.
Not to kick the hornet's nest, but I read that the Summit carb is a remake of the 4100, using a double fuel inlet where the 4100 uses a single, and that the boosters off the Summit Carb will interchange with the 4100.
With the 47s in the primaries it was running rich. I dropped way down to 44's and got a lean hesitation off idle. I installed 46's and the problem was solved.
Id like to look into them.
Elder User
Joined: Mar 2004
Posts: 747
Likes: 0
From: Klamath Falls OR
I'm having issues with mine idleing to high.
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Anybody got any ideas on how to get her to idle down a little bit more?
I can't get it to stay at 600rpm wants to hang around 7-900 rpm most of the time, I was wondering if my jets are to small causing a lean condition?
I haven't had the chance to check the plugs like was mentioned earlier, and I did spray some choke cleaner all around the carb and intake, and I didn't get any changes in rpm while doing that, so if its a vaccum leak it's a small one, I'll have to double check it again to make sure tho.
I also noticed that my butterfly's are sticking, so I gotta figure out how to repair that.
Anybody got any ideas on how to get her to idle down a little bit more?
So to set the secondary... It should be a 1/4 to 3/4 turn from the bottom in. So adjust it out (to where the butterflies just touch the throat). Now when the screw touches the lever. Turn it 1/4 to 3/4 of a turn in. That should fix it!