Autolite 1100 Venturi Mod

:unsure: one thing you might want to test before you invest lots of your time is how the PVC material reacts around gasoline. Don’t know the answer to that question. Good luck on your experiment. (y) :nod:
 
Couldnt you build the venturi body thickness up with a high temp putty, then bore it to the desired size?

JB Weld and Permatex both make a fuel tank repair putty that might work.

You would retain the needed bell shape on the top and bottom.
 
I'm liking these ideas. I did try playing with the eccentrics in my distributor but was unable to get them to budge. I also swapped around springs but that was at a point I didn't have the engine tuned properly. Perhaps I could try again. I'm not sure the distributor that is in the engine that's for sale in my area. I'm unable to tell from pictures and I have yet to see it in person. I did some reading over whether PVC was fuel resistant before I thought I'd go that route. I found info that said it was resistant to oils, detergents, and chemicals. That's when I realized we use it to flush anything and everything down the drains in this world. I think we even use certain kinds of acid to clear out plumbing drains. This had me convinced it would stand up to what I might throw at it. Only way to really tell will be over time though.

I like the idea of building the Venturi body up and using it but that might just be a last resort. Only because it's my save all for the experiment not working out. I found 1-1/4" PVC fit snugly into the throttle bore where the Venturi was located. It will need some shaping and tapering as I'm not planning on leaving it as a straight shaft. I will probably have to taper the lower side removing about 1/4" inside diameter so it will match the 1-7/16 throttle bore. I searched around to see if someone had a large tapered grinding stone I could put on the end of a drill for shaping the inside of the PVC but I was only able to find them large enough online. I will probably use a half round file to shape the inside of the pipe. The top side will be rounded over to help the airflow smoothly into the Venturi. After that I plan on cutting the grass plug I removed so it will flush up with the inside of the throttle bore. Then I will drill a very small hole with a #53 drill bit I picked up for the Venturi vacuum. If this size hole does not provide adequate vacuum I can enlarge it one step at a time. I'm pretty sure the jet said .59 so I will probably try to open that up as well.
 
With the venturi out, can you take a hole saw and run through it to open it up? May be easier than trying to build a new one. You could take sand paper and wrap around a piece of pipe or dowel and smooth the bore out after running a hole saw through it.
 
So, as previously stated the 1.1 Venturi 1100 was rated at 156 cfm and the 1.2 Venturi carb was rated at 186 cfm. If the Venturi is opened up by a small amount of .05 this should be good for another 15 cfm resulting in or around 200 cfm. If I could uniformly open the Venturi up to 1.375(1-3/8) this should flow between 210-215 cfm. At that point we are getting close to the flow rate of an Autolite 2100 with 1.01 Venturi. Any ideas on how to convert to annular discharge??? Lol....
 
jimlj66":33985rwy said:
With the venturi out, can you take a hole saw and run through it to open it up? May be easier than trying to build a new one. You could take sand paper and wrap around a piece of pipe or dowel and smooth the bore out after running a hole saw through it.

The stock Venturi is made of a thin plastic. Before removing this was one of my ideas, just open the stock version up but it just doesn't have the material in place to be able to do it. I did have the idea of opening the throttle bore up just a little. At that point I would need a throttle plate to match though. If this little experiment works out though a person, for very little money could open their stock 1100 up for a performance boost. Could even be done on a multi carb setup. With all my thought process lately I've wondered what two of these carbs ran synchronously and not progressively could do on one of our engines.....
 
Creechn32,

The concern with enlarging the Venturi too close to your throttle bore size of 1.4375” is not that you would lose velocity specifically, but that you would weaken the vacuum signal to the main fuel circuit, resulting in poor throttle response and fuel economy. The new insert you are making from PVC needs to imitate the profile of the stock insert you removed, with the narrowest part at the same height as the stock insert so that the booster Venturi cast into the air horn will still be able to amplify the vacuum signal.

All that being said, there is no harm in experimenting, so good luck and have fun!
 
Creechn32":14m1hhxq said:
jimlj66":14m1hhxq said:
With the venturi out, can you take a hole saw and run through it to open it up? May be easier than trying to build a new one. You could take sand paper and wrap around a piece of pipe or dowel and smooth the bore out after running a hole saw through it.

The stock Venturi is made of a thin plastic. Before removing this was one of my ideas, just open the stock version up but it just doesn't have the material in place to be able to do it. I did have the idea of opening the throttle bore up just a little. At that point I would need a throttle plate to match though. If this little experiment works out though a person, for very little money could open their stock 1100 up for a performance boost. Could even be done on a multi carb setup. With all my thought process lately I've wondered what two of these carbs ran synchronously and not progressively could do on one of our engines.....

The answer to your question is that two Autolites, 1904 Holley's, or severial others with solid linkage are about the perfect combo on a mild six build up. This was a faveriote of the Ford 223 Six Hot Rodder's in the 1950's and 60's, the carb's were moved from center of engines intake so that each carb was centered over a set of intake ports. Performance was very good and many claim to have even better economy than the stock single 1V.

On the Venturi experiment, remember that a Venturi works on the same principal as an air planes wing so shape needs to follow that. Good luck (y) :nod:
 
peeeot":2x3ia7l2 said:
Creechn32,

The concern with enlarging the Venturi too close to your throttle bore size of 1.4375” is not that you would lose velocity specifically, but that you would weaken the vacuum signal to the main fuel circuit, resulting in poor throttle response and fuel economy. The new insert you are making from PVC needs to imitate the profile of the stock insert you removed, with the narrowest part at the same height as the stock insert so that the booster Venturi cast into the air horn will still be able to amplify the vacuum signal.

All that being said, there is no harm in experimenting, so good luck and have fun!

I was actually thinking of just this earlier. I'm glad you reminded me. I was thinking it would do me well to have the exact height overall, and taper the interior to the same point, height, as in the original. I guess we will see if air speed will remain fast enough for proper operation. This has been mentioned once already so now I'm curious.
 
Working on some shaping and filing of the interior and exterior of the PVC. Im using a half round file. Had to taper the exterior just a little bit to get the PVC to slide down far enough to seat, basically the last 1/4" seemed to taper in just a small amount and wouldn't allow the PVC to seat all the way. From there I made a line on the interior at the same height of the narrowest part of the original Venturi for a tapering point. I filled the rest of the interior in, up to that point to know when I have reached the final point and not go further from that direction.

 
More profiling, sanding and shaping of the PVC. You can notice the beveling and shaping of the upper side of the Venturi. Did some research last night over Venturi and understand how the bottleneck in the Venturi increases air speed and in turn creates a drop in pressure. This is what creates the vacuum/suction of gas through the carburetor. I've tried to duplicate the point at which the bottleneck occurs, where the Venturi gets smaller. Hopefully we are still small enough to have enough air speed for the carburetor to still function correctly. You can also see the increase of inner diameter over the original Venturi. We still have a bottleneck compared to the carb inlet. Hopefully this change in diameter helps with the air speed. I believe I am done shaping on this piece of PVC for now. The next step for this carburetor will be a kit as it sat for a number of years before it came into my possession.

 
If you are to big on the bore you can buy a piece of 1.5in thin wall and cut through one wall on a table saw down the length until you remove enough material to compress it and force it inside the 1.25in tube.

I have done this before with good results. The thin wall in the freezer and a heat gun on the sch40 helps for a snug fit. If you cut just right the seam will be nice and tight.

That will give you a smaller inside diameter, the same outside diameter and give you more material to shape the bell.
 
Very nice piece of craftsmanship.
You really need to upgrade to a later distributor to take advantage of the extra CFM air flow.
Your 1/4" oil drive is the ???? Either bite the bullet on a DUI or ream the block to .517-.518" so you can use the 5/16" oil drive with an oil pump to match & a distributor @ half the cost.
 
This is a job for a 3d printer. With that venturi core you could model it and then alter the venturi size and shape all you want and print something that fits and just needs minimal work to smooth and make fit. Notches, holes and all
 
Is that enough venturi to function as a venturi?

At some point, the ratio size of the venturi to the main bore will fail to create enough vacuum differential to function.
 
wsa111":1wmkhguk said:
Very nice piece of craftsmanship.
You really need to upgrade to a later distributor to take advantage of the extra CFM air flow.
Your 1/4" oil drive is the ???? Either bite the bullet on a DUI or ream the block to .517-.518" so you can use the 5/16" oil drive with an oil pump to match & a distributor @ half the cost.

I guess the first step,will be to,see if this even works. There is always the possibility I install the carburetor and it won't even function properly. I'm hoping for the best but ya never know. Ignition upgrade has been on my mind since I've started tinkering with this engine. I've had to prioritize a few things for the car though and for me I had to do it before I got started or else I'd just go in circles. The car is in dire need of new suspension parts. In the rear and in the front. My goal with the engine was to just get it running properly before I really get into it. After that I have a transmission leaking like crazy on me. Once drivetrain was sorted I wanted better than stock suspension parts. I want to make the car fun to drive. In the meantime anything I was going to do to the engine was going to be transferable onto a 200. That's where my current resistance to an ignition upgrade, at least a $200-$300 dollar upgrade, comes in. If I upgrade this engine To a DSii or HEI it won't be transferable to a 200 down the road, or won't be ideal. In that respect, if I could improve airflow in and out of the engine while having a "good enough" ignition for the moment, the improvements I make can get used on a future engine. I did upgrade to a hotter coil. Do you know if an Accel super stock coil #8140 can be used with a Pertronix Ignitor?
 
The Accel coil will work fine. You will need a relay for a full 12V power for the coil.
 
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