How to make a venturi

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Model T Ford Forum: Forum 2017: How to make a venturi
Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 05:52 pm:

So, haven't heard from anyone with a U&J if they'd be willing to swap venturis with me. Looks like my best bet is going to be making another one myself.

What does the board recommend? How would you go about making one of these?







Looks like to me they had some sort of clamp for the outer ring and then stamped it. The upper round flat portion is noticeably thicker than the narrow edge. I believe this piece is brass, though I don't really care if I use a brass piece to duplicate it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Plank - Three Way, TN on Saturday, April 08, 2017 - 05:58 pm:

Can you make a dimensioned sketch of the part? I have a lathe and might be able to spin one out of some copper tubing. I would be willing to try it anyway. You would owe me a ride in your speedster then. If I fail, at least I tried.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 07:00 pm:



I think this tells you everything. Happy to answer any questions. There's basically 3 sections. From left to right is the flat section - this allows the venturi to sit on a lip inside the carb body. On that flat section it's perfectly flat for .175" (I didn't write clearly, the next diameter is .35" less than the 1.68" OD, so 1.33" diameter). Then begins a smooth turn in at about 45 degrees, this transition zone is .15" deep, or .11" if measuring from the backside of the flat lip. Then the 3rd zone the largest ID is .96", then a perfectly straight taper down to the smallest ID of .75".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 07:02 pm:

Honestly, even if you didn't exactly duplicate this part, if you were just able to make 2 following these dimensions and the 2 you made were darn near identical, I would just use the two new ones in both carbs.

Thanks Dennis! I really appreciate you trying.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donnie Brown North Central Arkansas on Saturday, April 08, 2017 - 07:05 pm:

Seth, I may have a trade for you. Give me at least till tomorrow before you go into full blown fabrication mode ... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 07:07 pm:



Sorry, ignore that first sketch. I fixed it but couldn't delete that picture in time.

Donnie! No problem. I really wasn't expecting anyone to have an answer this fast, but am excited that Dennis wanted to try something.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Saturday, April 08, 2017 - 07:07 pm:

Make a form and spin a new one from copper sheet. Do this on your lathe. If no late then a drill or drill press.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Plank - Three Way, TN on Saturday, April 08, 2017 - 07:12 pm:

I think I can make two alike. Let me know if you want me to proceed. Sounds like you might have a trade possibility.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 07:19 pm:



If you look at both photos you can see how the aluminum venturi is narrower at the bottom - it cuts off more of that small tube down in there at 3 o'clock. What you can't see but what I can feel with my finger is that the aluminum venturi is also longer, there's less of a gap between the bottom of it and the bottom of the inside of the carb.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 07:27 pm:

Dennis go ahead if you don't mind. If Donnie has an aluminum one then I may just try them both and see if one runs better than the other. The brass design might flow better but be hard to start, I don't know.

The brass one's carb serial number is F0684, where as the aluminum one's F23555. Maybe they're for different cars or maybe the aluminum one actually runs better. The aluminum venturi certainly seems like it would be harder/more expensive to make compared to the brass one.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donnie Brown North Central Arkansas on Saturday, April 08, 2017 - 10:50 pm:

Seth, I got around to looking at my carb today. It has an aluminum venture. How did you get yours to come out. ??? My carb also has some kind of a flanged ring that possibly holds the venture in place. I have it soaking in PB Blaster tonight. Ill try again tomorrow, but it is stuck tight. I have to proceed slowly as it looks like it would be very easy to damage the ring or the venture. Ill try and post pics of my carb tomorrow. I think I would like the larger venture on my single carb setup. And it may be that a smaller venture would be better for your dual carb setup. ???? But I am just guessing, with no idea if Im right or not ...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 11:16 pm:

Mine is stuck right too. Ha! The flanged ring is brass on both of my carbs and it just slid right out without much fuss. The brass venturi also came out pretty easily. But the aluminum one is tight as a tick. I am also soaking mine in PB Blaster. It has almost an interference fit. I'm not sure how to even get at it to persuade it out of there.

On the very bottom is an air passage that goes up to the small hole at 3 o'clock you see partially covered by the venturi. The problem is you need a really long, really skinny punch, and I'm afraid it'll hurt the venturi more than actually move it.

I think I'm gonna try to make a small puller. Some small hooks to get under the venturi and a bar across the top of the carb. I'll let you know how that turns out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 11:24 pm:

Here is the brass flanged spacer. It gives the throttle body portion something to press the venturi down with and is also a place for a gasket to sit.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 11:25 pm:

Whoops, here are the pics.






Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison - Rice, Minnesota on Saturday, April 08, 2017 - 11:26 pm:

It looks like a good product for someone with a small CNC bar machine. You'd probably only sell one every five years but...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Saturday, April 08, 2017 - 11:56 pm:

Mike, as often as I need the stuff I've decided I'm gonna buy all this shop equipment when I get the chance.

There's just too many cool things that need to be made.

With a laser scanner Faro arm and a big CNC machine with lots of axis and I'll be able copy and make darn near anything.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison - Rice, Minnesota on Sunday, April 09, 2017 - 12:00 am:

Okay, here's what I need: ...

:-)

Oh the faro arm will be nice but you might as well invest in a Coordinate Measuring Machine and a good 30" comparator too.:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Sunday, April 09, 2017 - 01:30 pm:

Seth, most of the time those venturis are pot metal and are virtually welded in place. No easy way to get them out and when you do a lot of times they will fall apart anyway.

OK, so here is Unca Stan's free advice. Take it for what you paid for it. Holly G venturis drop right in a fit. $25 from any supplier. If you have a lathe, take a little off the bottom to give it a little better air flow if you want. I don't. Just whack the original with a chisel and move on with the project. Or save the pieces and turn a new one. It takes about 15 minutes to make one out of Aluminum instead of fooling with it for days trying to get the old one out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donnie Brown North Central Arkansas on Sunday, April 09, 2017 - 02:52 pm:

Stan, Im not Seth, but great advice. I feared that it was pot metal. Pot metal usually swells, and makes it almost impossible to remove. I hope Seth will split the cost of what your advice and knowledge cost us. :-) :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donnie Brown North Central Arkansas on Sunday, April 09, 2017 - 02:52 pm:

Stan, Im not Seth, but great advice. I feared that it was pot metal. Pot metal usually swells, and makes it almost impossible to remove. I hope Seth will split the cost of what your advice and knowledge cost us. :-) :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Sunday, April 09, 2017 - 03:00 pm:

Ah ha! Awesome, while it may be free the advice is appreciated. I didn't know that the Holley G venturi was a drop-in replacement.

I'm gonna try the two that Dennis making, and if they don't work I'll nab two aluminum ones from Lang's.


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