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Autolite 1100 Venturi Mod

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Creechn32
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Autolite 1100 Venturi Mod

Post #1 by Creechn32 » Wed Feb 13, 2019 7:05 pm

So, I've been researching for a while. Reading through backlogs and backlogs on this forum. Great information and such a wide range of personal experience. My mind has been in overdrive. I've got an idea for modifying the removable Venturi on an SCV equipped 1100. The biggest difference between the 1100 and 1101 is the Venturi size and throttle bore. Throttle gore for the 1100 I know is 1 7/16. Venturi size on the carb I have in front of me is between 1.1-1.125, right under 1 1/8". My idea involves removing the current Venturi and using a piece of PVC pipe, some time, and some sandpaper to fashion a Venturi with at least 1.25-1.5" inner diameter. I did a little digging and ChampionCarbs sells a replacement Venturi for the 1100 but it's $89. A bit pricy I believe. Of course I could see needing a jet change also after modifying the Venturi. So far my next step is to remove, without damaging, the existing Venturi to better understand if I might be able to modify it, if the walls are thick enough or replace it with something else. This is an idea I have as a step around not being able to upgrade distributors for less than $400.00 as my 170 engine has the 1/4" oil drive and a DSii conversion isn't possible for less expense. What is everyone else's thoughts on this. I even thought if possible I could find someone to turn me a Venturi on a lathe out of aluminum. Wondering if anyone sees any flaws in what I'm thinking, what might or might not work, and possible solutions???
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #2 by CZLN6 » Wed Feb 13, 2019 7:25 pm

Howdy Creechin:

I like the way you think. I can tell you that I have tried to remove the plastic venturi insert from a '65 200 1100 carb. No success. I destroyed the insert in removing it. I couldn't figure how the insert was installed and secured. If it was glued in I found no evidence. So, I wish you luck and hope that you will your success and/or?????

I tried heat. No luck. Keep us posted.

Adios, David
co-author of the Falcon Performance Handbook
http://www.falcon6handbook.com/

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wsa111
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Re: Autolite 1100 Venturi Mod

Post #3 by wsa111 » Wed Feb 13, 2019 8:43 pm

David, Jon at Pony Carbs used to install a 223 six venturi insert in the 1100 that i still own.
I believe the main jet is a .069".
The venturi insert is held in by having the main body staked in several areas.
The venturi vacuum tube also is inserted through the plastic insert.
Maybe the present owner of Pony Carbs can help you. Bill
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, DSII dist. MSD-6al & TFI Coil. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Creechn32
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Re: Autolite 1100 Venturi Mod

Post #4 by Creechn32 » Wed Feb 13, 2019 9:40 pm

I noticed the three indentations and the vacuum port. Removing the vacuum tube might take a bit of ingenuity but a file or dremel should take care of the pressure points formed to keep the Venturi in place.

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1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #5 by wsa111 » Wed Feb 13, 2019 10:39 pm

If you want to delete the SCV this is the time to convert it to ported vacuum. With ported you delete the venturi vacuum tube & plug the exit with a 6-32 brass set screw.
There is a link on this forum in the tech section on the other 2 blocked ports.
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, DSII dist. MSD-6al & TFI Coil. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Georgia200
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Re: Autolite 1100 Venturi Mod

Post #6 by Georgia200 » Wed Feb 13, 2019 11:28 pm

Another option may be to swap the guts from a 68 distributor into your 170 distributor body.

I think thats how the Y-block guys get away from the LOM. Im not sure if it would work on a Falcon Six, but its worth looking into.

I think for this to work they both have to be Motorcraft distributors. If your 170 distributor is an Autolite, then it will not work.

That would get you away from the LOM, then you can modify your carb or buy a later non SCV carb.

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Re: Autolite 1100 Venturi Mod

Post #7 by Creechn32 » Thu Feb 14, 2019 6:25 am

wsa111 wrote:If you want to delete the SCV this is the time to convert it to ported vacuum. With ported you delete the venturi vacuum tube & plug the exit with a 6-32 brass set screw.
There is a link on this forum in the tech section on the other 2 blocked ports.



Part of my motivation for doing this is searching for a modification that will work along side of the LOM distributor. There's a lot of ideas I have for my current engine but they are all curtailed by difficulty in swapping the distributor. I've also wondered if I could swap a later vacuum diaphragm on the LOM distributor that would function off ported vacuum. Really, other than the lack of mechanical advance, the biggest downfall to the LOM is it runs off Venturi vacuum and the SCV. If the diaphragm was able to be swapped to a later ported style that was adjustable would that not also help to solve this issue? All this thinking revolves around me wanting to be able to add a 2 barrel carburetor. Whether by adapter plate or modified head, the issue becomes none of them will function with the LOM and Venturi vacuum. At the same time not wanting to spend $400 on an HEI to fit in its place. There is also an Aussie electronic distributor alternative, for less money, to the LOM but information about it has been difficult for me to find. My mind has really been thinking about a synchronous dual carb setup on a log manifold. All my thinking has led me to searching for 1101's equipped with an SCV but they seem to be like unicorns currently, or super expensive. So, in my quest for an alternative carburetor for improved airflow, that works with the LOM, I have arrived at this point. The 1100 has a removable Venturi, why don't we just open it up? Airflow should be able to increase at least to the size of the throttle bore. Once again, someone correct me if my thinking is off. I'm not 100% when it comes to the science of airflow and airflow characteristics when it comes to porting heads, intake runners , and the like. I've done a ton of reading online for a few years now. I understand air does funny things sometimes. All my rambling aside, if the Venturi is able to be opened up, I see no reason why an 1100 couldn't flow just as much air as an 1101. For those without an SCV equipped carb it should be even easier, if it's successful.....
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #8 by bubba22349 » Thu Feb 14, 2019 12:17 pm

Creechn32 wrote:
wsa111 wrote:If you want to delete the SCV this is the time to convert it to ported vacuum. With ported you delete the venturi vacuum tube & plug the exit with a 6-32 brass set screw.
There is a link on this forum in the tech section on the other 2 blocked ports.



Part of my motivation for doing this is searching for a modification that will work along side of the LOM distributor. There's a lot of ideas I have for my current engine but they are all curtailed by difficulty in swapping the distributor. I've also wondered if I could swap a later vacuum diaphragm on the LOM distributor that would function off ported vacuum. Really, other than the lack of mechanical advance, the biggest downfall to the LOM is it runs off Venturi vacuum and the SCV. If the diaphragm was able to be swapped to a later ported style that was adjustable would that not also help to solve this issue? All this thinking revolves around me wanting to be able to add a 2 barrel carburetor. Whether by adapter plate or modified head, the issue becomes none of them will function with the LOM and Venturi vacuum. At the same time not wanting to spend $400 on an HEI to fit in its place. There is also an Aussie electronic distributor alternative, for less money, to the LOM but information about it has been difficult for me to find. My mind has really been thinking about a synchronous dual carb setup on a log manifold. All my thinking has led me to searching for 1101's equipped with an SCV but they seem to be like unicorns currently, or super expensive. So, in my quest for an alternative carburetor for improved airflow, that works with the LOM, I have arrived at this point. The 1100 has a removable Venturi, why don't we just open it up? Airflow should be able to increase at least to the size of the throttle bore. Once again, someone correct me if my thinking is off. I'm not 100% when it comes to the science of airflow and airflow characteristics when it comes to porting heads, intake runners , and the like. I've done a ton of reading online r a few years now. I understand air does funny things sometimes. All my rambling aside, if the Venturi is able to be opened up, I see no reason why an 1100 couldn't flow just as much air as an 1101. For those without an SCV equipped carb it should be even easier, if it's successful.....


Sorry but the later model vacuum canisters won't fit the LOD and even if they did it wouldn't change its operation to be of any benefit. Next wether you use a venturi vacuum or a ported vacuum source under power the engines vacuum is going to drop and with that the vacuum controled advance of the LOD this is just the opposite of what is needed for good performance. It's also why the later models 1967 Calif. and all 1968 Ford Six engines up all used a distributor with both mechanical advance for better power / performance and a vacuum advance system for best economy. Even with a Pertronix installed (a good mod that helps quite a bit) or the use of the electric MoPar control box another good mod that I have also used the operation of the LOD advance system isn't good for a performance work. So in my opinion a LOD should only be used for a totally stock restoration, since there are much better units available for a performance build up, you need to ditch the LOD because they don't have the better mechanical advance. This was a first step mod even back when these engines were stil relatively new, back then there were dual point distributor's with mechanical advance only (by Mallory) to solve this problem today there are even better choices. Below is a group of posts that discuss most of the options for the early engines that used the 1/4 inch drive LOD. To me if you have the block apart for rebuilding then the best way is to machine the block to fit the late model DuraSpark II. If the engine isn't apart there are a number of other ways to do this swap and they should come out cheaper than a DUI. Good luck :thumbup: :nod: Edited

1/4 inch Distribitor swaps
viewtopic.php?f=1&t=77360&p=595417&hilit=1%2F4+inch+Distribitor+swap#p595407
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Autolite 1100 Venturi Mod

Post #9 by Creechn32 » Thu Feb 14, 2019 12:20 pm

I read through that post not long ago. Question would be has anyone done it or just in theory? Reading through it again I wonder what the cost comparison between a DSii conversion, machining of the distributor end, and an oil pump plus shaft is to just an HEI distributor with 1/4 drive....
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #10 by bubba22349 » Thu Feb 14, 2019 12:42 pm

Yes this has been done by a few site members it's not a theory it's basic machine shop practices. I don't know how hard it is to find a competent machineist in your area though, but I was doing this type machine shop work back in high school in the mid 1960's. A new Melling M 65 oil pump that also comes with a new 5/16 inch oil pump drive shaft is about $75.00 this is usually a normal replacement item anyway during a rebuild, a rebuilt DSII can range from $50.00 to $90.00, I used to sorce a complete DSII system (distributor, plug wires, coil, wire harness, ICM) from the local pick a part cheap $25.00 to $35.00. You could get a calabrated DSII for about $230.00 but you should contact Bill wsa11 (in above posts) to verify this cost. Also not a theory is the fact that the Australian Ford small sixes for many years used a hybrid distributor that was a combo of the early 1/4 inch drive distributor OD shaft size with a 5/16 inch hex broched drive socket plus the M 65 type oil pump with the 5/16 inch oil pump drive shaft. Good luck :thumbup: :nod: Edited
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Autolite 1100 Venturi Mod

Post #11 by bubba22349 » Thu Feb 14, 2019 1:10 pm

There is another couple of meathods too using the Ford EDIS waste spark system. Check out the posts by the "sameguy" where he adapted the EDIS from start to finish. Last is if you were lucky enough locate one of the old Mallory dual point distributors that were made for the early 1/4 inch oil pump drive engines (144, 170, pre 1965 200) though they are probably a rare item in this day and age. Good luck. :thumbup: :nod: Edited

Ford EDIS
viewtopic.php?f=98&t=67718&hilit=Ford+Edis#p518607
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Autolite 1100 Venturi Mod

Post #12 by wsa111 » Thu Feb 14, 2019 4:59 pm

Get your machine shop to ream the distributor shaft bore to .517"-.518" so you can go with a DS1 or a DS11 distributor & convert your carb to a non SCV state as i previously mentioned.
The only difference between the DS1 & The DS11 is the size of the cap, both use the same housing.
Bubba mentioned the old Mallory unit which will fit your block without being modded, or go with the DUI which offers the 1/4" oil pump hex drive.
I can recurve your loadamatic using my Sun Distributor Tester which has a vacuum pump to help in a recurve. Don't expect a miracle though.
Then install the Pertronix conversion with a newer coil which will help.
Any way you go unless you want to live with the loadamatic get your wallet out.
I would go with a later 200 engine & that will save $$$ in the long run. Good luck. Bill
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, DSII dist. MSD-6al & TFI Coil. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Re: Autolite 1100 Venturi Mod

Post #13 by Creechn32 » Thu Feb 14, 2019 7:39 pm

wsa111 wrote:Get your machine shop to ream the distributor shaft bore to .517"-.518" so you can go with a DS1 or a DS11 distributor & convert your carb to a non SCV state as i previously mentioned.
The only difference between the DS1 & The DS11 is the size of the cap, both use the same housing.
Bubba mentioned the old Mallory unit which will fit your block without being modded, or go with the DUI which offers the 1/4" oil pump hex drive.
I can recurve your loadamatic using my Sun Distributor Tester which has a vacuum pump to help in a recurve. Don't expect a miracle though.
Then install the Pertronix conversion with a newer coil which will help.
Any way you go unless you want to live with the loadamatic get your wallet out.
I would go with a later 200 engine & that will save $$$ in the long run. Good luck. Bill


My thoughts are to eventually go to a 200 but for now I was wanting to do what I can before I start sinking my real money into the suspension parts this car really needs....

I am more interested at the moment of squeezing what I can out of the current setup. There is a 200 C4 combo not far from me for $325 on Facebook. I am also looking towards the future with this carburetor. I have already upgraded to a hotter coil in this car. An Accel superstock coil replaced the stock coil when I replaced everything else ignition wise. Now I'm wanting to experiment carbwise.
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #14 by Georgia200 » Thu Feb 14, 2019 10:28 pm

With a 1.5 carb hole and 170 ci, you are really just throwing money away looking for performance.

I would snag the 200/C4 and build that at your leisure and keep the 170 on the road.

I find that when someone takes a running car off the road, there is a good chance it never goes back on the road.

I bought my 67 in Oct and kept it running. Ive been working on the 5 lug swap for 5 months now and Im still a weekend or two from being ready to make the swap happen.

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Re: Autolite 1100 Venturi Mod

Post #15 by Creechn32 » Thu Feb 14, 2019 11:07 pm

Georgia200 wrote:With a 1.5 carb hole and 170 ci, you are really just throwing money away looking for performance.

I would snag the 200/C4 and build that at your leisure and keep the 170 on the road.

I find that when someone takes a running car off the road, there is a good chance it never goes back on the road.

I bought my 67 in Oct and kept it running. Ive been working on the 5 lug swap for 5 months now and Im still a weekend or two from being ready to make the swap happen.


Car is currently on the road. I've been enjoying driving it. This carburetor is one I bought off a guy not far from me. An experiment really. Something to mess with. What's the worst that could happen, it not work out? I will try to keep the original Venturi intact that way if my way doesn't work I can return the carburetor to original form. But the 1101 is worth about 5hp from what I've read and it only has a 1.29 Venturi, if my memory serves me correctly, and 1.5 would be better than that. Besides, if it works out I can use it on a 200 at a later date.
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Autolite 1100 - '68+

Post #16 by chad » Fri Feb 15, 2019 9:20 am

don't 4get to 'source over into' the '65 models for the bigger dizzy hole in the block (many don't recommend the DUI) so U can go w/the DSII (post '67 for oe equiped non SCV/LOM - but those R easy to swap out).
:thumbup:
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Re: Autolite 1100 Venturi Mod

Post #17 by peeeot » Sat Feb 16, 2019 1:24 am

Creechn32,

In order for a carburetor to work, there has to be a certain pressure difference between the inside bore of the carburetor where the fuel discharge nozzle is and atmospheric pressure outside of the carburetor. This pressure difference is what pushes the fuel into the airstream.

A Venturi is a narrowing in the carburetor bore that increases air velocity and reduces pressure relative to the conditions present at the wider parts of the bore. By enlarging the Venturi of a carb, you reduce the velocity through the Venturi and thus decrease the pressure differential it generates.

Every aspect of the main fuel circuit of the carb is calibrated based on the Venturi size and the expected air flow through the carb at different engine speeds and loads. So, if you enlarge the Venturi, the carb will probably flow more air, but it will require more calibration than a jet change alone to function properly. If the Venturi is opened up to the same size as the throttle bore, you lose the Venturi effect entirely, and fuel will not discharge or atomize very well. The engine may still run but throttle response and fuel economy may be poor.

Additionally, any changes to the Venturi will alter the vacuum signal used to operate your LOM advance, which will require distributor recalibration to recover the “liveliness” of the advance curve.

Is your carburetor marked 1.20 on the side? This was the largest 1100 venturi Autolite used. 170s came with 1.10 Venturi size stock.

You can make a noticeable difference in how lively the car feels just by improving your loadomatic distributor calibration. You can change the springs and the preload on the springs, the total advance range, and the initial advance. Manipulating these for a shorter, tighter curve with more initial advance than stock will make the engine feel more eager.

It’s worth experimenting with your main jet too. If the carb is calibrated too lean for e10 gasoline, there is noticeable improvement to be had by getting the mixture right.

I hope this helps.

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Re: Autolite 1100 Venturi Mod

Post #18 by Creechn32 » Sat Feb 16, 2019 11:04 am

peeeot wrote:Creechn32,

In order for a carburetor to work, there has to be a certain pressure difference between the inside bore of the carburetor where the fuel discharge nozzle is and atmospheric pressure outside of the carburetor. This pressure difference is what pushes the fuel into the airstream.

A Venturi is a narrowing in the carburetor bore that increases air velocity and reduces pressure relative to the conditions present at the wider parts of the bore. By enlarging the Venturi of a carb, you reduce the velocity through the Venturi and thus decrease the pressure differential it generates.

Every aspect of the main fuel circuit of the carb is calibrated based on the Venturi size and the expected air flow through the carb at different engine speeds and loads. So, if you enlarge the Venturi, the carb will probably flow more air, but it will require more calibration than a jet change alone to function properly. If the Venturi is opened up to the same size as the throttle bore, you lose the Venturi effect entirely, and fuel will not discharge or atomize very well. The engine may still run but throttle response and fuel economy may be poor.

Additionally, any changes to the Venturi will alter the vacuum signal used to operate your LOM advance, which will require distributor recalibration to recover the “liveliness” of the advance curve.

Is your carburetor marked 1.20 on the side? This was the largest 1100 venturi Autolite used. 170s came with 1.10 Venturi size stock.

You can make a noticeable difference in how lively the car feels just by improving your loadomatic distributor calibration. You can change the springs and the preload on the springs, the total advance range, and the initial advance. Manipulating these for a shorter, tighter curve with more initial advance than stock will make the engine feel more eager.

It’s worth experimenting with your main jet too. If the carb is calibrated too lean for e10 gasoline, there is noticeable improvement to be had by getting the mixture right.

I hope this helps.


So, this is not the original carburetor to my engine and is not the carburetor currently running on my engine. I say that so you know I'm not going to ruin something vital to the current state of my engine. This is a carburetor, that has the 1.1 Venturi, that I picked up for less than $50. You sound a little more up to speed on Venturi and air speed effect in a carburetor so I'll run my thinking by you. I've read quite a bit on these engines, carburetor, heads, and intakes. My question at this point would be: Will air speed through this engine decrease that much by increasing a single inlet from 1.1 to 1.25-1.5? I would think this single inlet would still carry more air speed than a 2v carburetor. I understand that I will have to fiddle with vacuum signal to distributor and carb jetting at the same time. My current initial advance settings and timing issues are completely covered in a previous post I had (1963 170 hesitation issues). This whole carburetor Venturi mod is an experiment of mine. I am going to try and save the stock Venturi. This is vital to me being able to return the carburetor to usable state if my experiment doesn't work. I say all this to let everyone understand that this isn't a modification to my car as much as it is an experiment to see if it's possible. Don't worry about my car and its current state as I have a working 1100 that will remain untouched to keep my vehicle in a state of being street worthy if this Venturi mod doesn't work. What I was hoping from this post were ideas of how to make this mod work, definitive proof it won't work, or workable ideas to make it work. I'm not going to back myself into a corner of my vehicle being inoperable with this experiment. I say all that just so we are all on the same page. If this works it could be a very easy inexpensive modification to the more abundant Autolite 1100 and a stock head. Also, just because I have yet to upgrade the ignition to a DSii or HEI doesn't mean this modification, if successful couldn't work along side an ignition upgrade. Ignition and engine upgrade are not the subject of this post however. But I do appreciate all the invaluable knowledge, experience, and wisdom when it comes to those subjects though. I hope everyone is enjoying their Saturday.....
1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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Re: Autolite 1100 Venturi Mod

Post #19 by Creechn32 » Sat Feb 16, 2019 4:19 pm

Update: took some fiddling to get the Venturi out without damaging. After Venturi is out you can see the brass vacuum port pressed into where the Venturi vacuum was. Applied a small bit of heat from a propane torch around the area and pressed the brass piece out with a pair of channel locks. 1-1/2" PVC didn't work too well. Going to try 1-1/4" PVC next.

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1963 Ford Falcon 4 door: 170/2sp automatic, all original except paint, in need of front and rear bumpers and brackets, soon to upgrade suspension
Newton, NC

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